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Edmond Locard, who lived from 1877 to 1966 and was called the Sherlock Holmes of Lyon, set up one of the first police laboratories in 1910 in two attic rooms of the Lyon police department, with little more than a microscope and a basic spectrometer. His central idea, now known as Locard's exchange principle, holds that a criminal cannot enter a scene without leaving something behind and carrying something away. The episode uses examples like leaning on a freshly painted wall to show how fibers, skin cells and soil move in both directions without anyone noticing.

In 1953 Paul L. Kirk formalized Locard's idea and described physical evidence as a silent witness that, unlike human memory, does not forget or lie. The hosts look at why cases still go cold when the evidence is always there, how modern crime scene teams lock down and map a room, and how the same principle now drives digital forensics. They also trace Locard's influence across detective fiction and television.

• How glass fracture patterns reveal the direction of an impact and wire cutters leave tool marks like a ballistic signature
• Kirk's argument that unsolved cases come down to human failure, not missing evidence
• Why police tape exists to freeze the exchange and stop new contamination
• Logs, digital signatures and IP routing histories as the cyber version of a muddy boot print
• Gil Grissom invoking Locard on CSI, and Locard himself appearing in The Sister Boniface Mysteries

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In 1946 Jean Harris heard Put the Blame on Mame at the movies, and the song played in her head for the next 33 years. This episode explores the earworm, a term from the German Ohrwurm, known clinically as involuntary musical imagery. It is a memory loop, not a hallucination, and the hosts separate it from palinacousis, a rare condition tied to temporal lobe damage. About 98 percent of people get earworms. Men and women get them equally often, but women's last longer and bother them more, and people who score higher in neuroticism or have intrusive thoughts get more of them.

Research shows that cheerful and somber instrumental music get stuck equally often, but negative tunes cause more distress. Nearly 75 percent of earworms have lyrics, usually a 15 to 30 second chorus, and the formula combines a fast tempo, a simple melody and one unexpected interval that trips the brain's predictive coding. The hosts also cover when a nonstop loop can be a warning sign and the science behind getting rid of one.

• The most reported culprits, from Don't Stop Believin' and Bohemian Rhapsody to Bad Romance and other Lady Gaga hits
• Climber Joe Simpson, injured and alone in the Peruvian Andes, unable to escape Boney M's Brown Girl in the Ring
• Why a loop with no break for more than 24 hours has, in rare cases, signaled a stroke, epilepsy or a tumor
• Mark Twain's 1876 jingle story, Alfred Bester's The Demolished Man and Emperor X's 10,000-year earworm for nuclear waste warnings
• Puzzles, chewing gum, playing the song to the end, and cure songs like Happy Birthday

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In 1916 Dr. Joseph Goldberger, his wife Mary and his assistant injected themselves with the blood of pellagra patients and swallowed their secretions, all to prove they could not catch the disease. This episode follows how he got there. Born in 1874 to a Jewish family in Hungary, he arrived in New York in 1883, grew up on the Lower East Side, started out in engineering at City College, and earned his M.D. in 1895. As an officer of the Marine Hospital Service he inspected immigrants at Ellis Island and fought yellow fever in Mexico, typhus in Puerto Rico and dengue in the South before Surgeon General Rupert Blue assigned him to pellagra in 1914.

By 1912 South Carolina alone was reporting 30,000 cases, and the medical establishment was sure a germ was to blame. Goldberger noticed that hospital staff never caught it, changed the diets at orphanages and the Georgia State Sanitarium with dramatic results, and then ran a prison trial that still raises hard ethical questions. Even after the filth parties, critics kept moving the goalposts.

• Two orphanages where 172 children had pellagra, and only one new case appeared in two years on a better diet
• Asylum patients with dementia who recovered so fully that they were discharged
• Governor Earl Brewer's pardon deal at the Rankin State Prison Farm, where five of 11 men had pellagra by six months and some were refused permission to quit
• Seven filth party trials with 16 volunteers, and not one case of pellagra
• Four Nobel Prize nominations, a pension for his widow, and Nazi defendants at Nuremberg citing Paul de Kruif's account of his prison experiment

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Between 1906 and 1940 pellagra struck roughly three million Americans and killed more than 100,000, progressing through the four Ds: dermatitis, diarrhea, dementia and death. The episode explains it as a deficiency of niacin, vitamin B3, and of tryptophan, and traces it back to Gaspar Casal's 1735 description of Asturian leprosy in Spain and the outbreaks in northern Italy, where more than 100,000 people had it by the 1880s. The common thread was corn. Indigenous cultivators in the Americas had long soaked kernels in lime water, a process called nixtamalization that frees the niacin, but Europeans took the seeds without the method.

In the American South the disease became known as spring sickness. Sharecroppers trapped growing cotton lived through winter on cornmeal and molasses, and the Beall degerminator of 1901 stripped what little nutrition the milled corn had. Assigned in 1915, Joseph Goldberger noticed that asylum inmates fell ill while staff did not, cured patients by improving their meals, and then induced the disease in healthy prisoners on a restricted diet.

• The Casal collar, the sunburn-like band of dermatitis around the neck
• Orphanage data showing that only children aged six to 12, too old for milk and too young for work rations, were getting sick
• The Rankin Prison Farm trial: 11 volunteers promised pardons, with six developing lesions after about five months
• Conrad Elvehjem's 1937 black tongue research in dogs and Tom Spies proving niacin cured human pellagra
• Why women historically got pellagra at about twice the rate of men, and where the disease still appears today

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Dolly the sheep was born on July 5, 1996, at the Roslin Institute in Scotland, the only surviving lamb from 277 attempts. Frogs had been cloned in 1958, but scientists believed a specialized adult cell was locked for good. The Roslin team, funded by PPL Therapeutics and the Ministry of Agriculture, used somatic cell nuclear transfer: an emptied egg from one ewe, the nucleus of a mammary gland cell from another, a small electric shock to restart development, and a surrogate to carry the pregnancy. Because the donor cell came from a mammary gland, she was named after Dolly Parton, and her existence was kept secret until February 22, 1997.

Dolly never left the Roslin Institute, slept indoors every night for security, and bred normally, producing six lambs. She developed arthritis at four and was euthanized on February 14, 2003, at age six with a lung cancer caused by the retrovirus JSRV. Her short telomeres fed a born-old narrative, but a 2016 study of 13 cloned sheep found they aged normally. The episode follows her legacy into pet cloning, conservation and stem cell science.

• Bonnie in 1998, twins Sally and Rosie, and triplets Lucy, Darcy and Cotton in 2000
• Why the indoor barn, not cloning, likely explains the lung disease that killed her
• Commercial cloning prices of about 50,000 dollars for a dog, 30,000 for a cat and 85,000 for a horse
• The Pyrenean ibex cloned in Spain in 2009, which died shortly after birth from lung defects
• The first cloned macaques in China in 2017 and five gene-edited clones in 2019, leading to induced pluripotent stem cells

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Colin Pitchfork, born in 1960 and raised in Leicestershire, earned the Chief Scout's Award, represented the UK at the 1975 World Scout Jamboree in Norway, married a social worker and became a skilled wedding cake decorator. He also had convictions for indecent exposure from age 17. In November 1983 15-year-old Lynda Mann was raped and murdered, and the only lab result available, a blood type shared by about 10 percent of men, could not identify anyone. In July 1986 Dawn Ashworth, also 15, was killed in the same way, and police pressured 17-year-old Richard Buckland, who had learning difficulties, into a confession to her murder while he denied the first.

Doubting that confession, detectives turned to Alec Jeffreys at the University of Leicester and asked more than 5,000 local men to give blood or saliva. Pitchfork paid bakery colleague Ian Kelly 200 pounds to take the test in his name. The scheme collapsed when Kelly mentioned it at the Clarendon pub and coworker Jackie Foggin reported it. The episode then follows Pitchfork's life sentence and the decades of parole battles that followed.

• The June 1986 night Pitchfork drove Liz Knight home and warned her never to accept a lift from a stranger
• How DNA profiling first cleared an innocent suspect before it caught a guilty one
• His wife's reaction as he confessed in their living room in September 1987
• A 30-year minimum term cut to 28, braille music transcription and a sculpture pulled from the Royal Festival Hall in 2009
• Release in September 2021, recall that November, a 2023 parole blocked by the Lord Chancellor and detective David Baker's warning

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Polio is ancient, from Egyptian art showing withered limbs to a 4,000-year-old skeleton in the United Arab Emirates, yet its great epidemics came in the 20th century. The episode explains why: for most of history infants met the virus while still protected by maternal antibodies, and modern sanitation delayed that first exposure until children were older and far more likely to be paralyzed. About 75 percent of infections cause no symptoms and only a small fraction reach the motor neurons, so silent carriers spread it widely. In the United States the 1952 epidemic brought nearly 58,000 cases, more than 3,000 deaths and over 21,000 people left with some paralysis.

When bulbar polio stopped patients breathing and iron lungs ran out during a 1952 outbreak in Copenhagen, anesthesiologist Bjorn Ibsen used tracheostomies and hundreds of medical students squeezing bags by hand, the forerunner of the modern intensive care unit. The hosts then compare Jonas Salk's killed injected vaccine with Albert Sabin's live oral drops, follow the Global Polio Eradication Initiative, and explain how vaccine-derived strains came to outnumber wild polio.

• Why paralysis risk climbs from about one in a thousand young children to one in 75 adults
• William Hammond's 1950 trial using gamma globulin from survivors, about 80 percent effective against paralysis
• Salk's vaccine as homeland defense and Sabin's as border patrol in the gut
• From roughly 350,000 paralyzed children in 1988 to 30 wild cases in 2022, with wild virus endemic only in Pakistan and Afghanistan
• The fake hepatitis B vaccination campaign that damaged trust, and the genetically stabilized nOPV2 licensed by WHO in December 2023

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Why does waking at 3 a.m. feel so different from waking at 7, even after the same amount of sleep? This episode explains what makes a rhythm truly circadian. In 1918 J.S. Szymanski kept animals in constant darkness and found they still held a 24-hour cycle, and in 1954 Colin Pittendrigh showed that the clock timing fruit fly hatching kept pace even in the cold. From those experiments come the rules: a circadian clock must be free-running, temperature compensated and entrainable by a zeitgeber, the German term for a time giver such as morning light reaching the suprachiasmatic nucleus through special light-sensing ganglion cells in the eye.

The story then goes down to single cells. Gene Block's work on isolated mollusk neurons showed the clock is cell-autonomous, and the 2017 Nobel Prize recognized the PER and TIM feedback loop that works like a molecular hourglass. The hosts explain why a 2 a.m. meal can reset the liver's clock while the brain stays on night time, how monarch butterflies and blind mole rats use their clocks, and what happens to mice and hamsters whose clocks are broken or mismatched.

• Monarch butterflies that fly the wrong way when the clocks in their antennae are altered
• Svalbard reindeer that abandon daily rhythms through months of constant light or dark
• Mice with deleted clock genes that overeat and become obese, and the leptin signal that stops getting through
• Tau mutant hamsters with 22-hour clocks forced into a 24-hour day and the heart and kidney disease that followed
• Chronotherapy research on timing ACE inhibitors at bedtime and short-acting statins in the evening

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A hemispherectomy removes or disconnects one entire half of the brain, and this episode traces how that radical idea became a standard treatment for children with severe drug-resistant epilepsy. Walter Dandy performed the first one in 1928 to remove a glioma, Kenneth McKenzie used it for intractable epilepsy in 1938, and in 1950 R.A. Krynauw in South Africa reported striking improvements in children with infantile hemiplegia. Then, in 1966, Oppenheimer and Griffith documented what the empty cavity did over the years: superficial hemosiderosis from repeated microscopic bleeding and dangerous obstructive hydrocephalus.

Theodore Rasmussen's functional hemispherectomy left the tissue in place but cut its connections, and later hemidecortication and the hemispherotomy developed by Delalande and Villemure refined the approach further. The hosts walk through who qualifies, from hemimegalencephaly to Rasmussen's encephalitis, how surgeons map the seizure source, what the operation costs the patient in vision and fine motor control, and how the remaining hemisphere rewires itself through neuroplasticity.

• Children who arrive with dozens or even hundreds of seizures a day that no medication can stop
• Why every technique, old and new, yields seizure freedom of roughly 70 to 75 percent, and why the ILAE prefers hemispherotomy
• Severing the corpus callosum and the permanent loss of half the visual field in both eyes
• Modern risks: hydrocephalus in 14 to 23 percent of cases, mortality under 1 to 2.2 percent, and reoperation around 4.5 percent
• Long-term outcomes, including walking, reading, the HOPS prediction scale and about one fifth of patients finding employment

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Charles R. Drew was born in 1904 in Washington, D.C., grew up in Foggy Bottom, and as a boy delivered more than a thousand newspapers a day. After Dunbar High School and an athletic scholarship to Amherst, he spent two years at Morgan College in Baltimore as a chemistry and biology professor, athletic director and head football coach to pay for medical school. Rejected by Howard and deferred by Harvard, he went to McGill in Montreal, graduated second of 127 in 1933, and began studying shock with John Beattie. At Columbia his thesis, Banked Blood, showed that plasma separated by centrifuge could last two months, and in 1940 he became the first African American to earn a Doctor of Science in Medicine there.

Recruited by John Scudder, Drew ran the Blood for Britain project, then became director of the first American Red Cross blood bank in February 1941. When the Army and Navy first refused Black donors and then ordered their blood labeled and stored separately, Drew called the policy scientifically baseless and resigned in 1942. He died after a car crash on April 1, 1950, on his way to a free clinic in Tuskegee, and the episode separates the facts of that night from the enduring myth that a whites-only hospital turned him away.

• Why stored whole blood spoils and how ruptured red cells release potassium that can stop a heart
• Blood for Britain's numbers: almost 15,000 donors and more than 5,500 vials of plasma shipped across the Atlantic in five months
• Drew's refrigerated mobile donation stations, the forerunner of today's bloodmobile
• His lifelong exclusion from the District of Columbia chapter of the AMA despite his achievements
• Survivor John Ford's account from Alamance General Hospital, and why the myth repeated on MASH felt so believable