Scientists make a startling discovery in the Antarctic, a Yeti-like snow creature frozen in a block of ice! Meanwhile, Jerry informs Sam, Clover and Alex that there have been reports of a strange being terrorizing a posh ski resort. When they arrive to investigate the luxurious place, they find that they aren't the only ones on the case until they meet Martin Mystery, a teenage paranormal investigator working for the Center – an organization much like WOOHP!

In the B-story, the girls all develop a different relationship with Martin;

Clover was initially hit on by Martin and tried to flirt with him, but got rejected.

Sam was compared to Martin's step-sister, Diana Lombard, much to her annoyance.

Alex started to bond with Martin over their love for video games.

Diana learns that CIHL stands for "Creature Intelligence Hybrid Laboratory" and starts to fight against it. However, she becomes overpowered by monsters who were once Octavia Paine's agents (Octavia Paine just used her). She was turned into a half-lizard, half-girl hybrid by Octavia Paine, a former Center agent who also did not get a good evaluation. Then Octavia creates the "Ultimate Monster" from the stolen monsters and sends it to get revenge on M.O.M. Martin and Diana work as a team to defeat it. In the end, Diana got an upgraded evaluation while Martin got a downgraded evaluation and the Center welcomed her back, making things go back to normal.

Diana resigns from The Center for not having a good evaluation and joins a rival paranormal organization called the CIHL and starts stealing Martin's monsters.

Diana decides to resign from The Center and joins CIHL and shocks Martin, Java, Billy, M.O.M. and the members of The Center. After being armed with CIHL gears and weapons, she goes after Martin's assigned monster. Let's just say this is a transformation.

Marvin escapes from an angry and temperamental leprechaun and calls Martin and Diana for help. It turns out that Marvin was keeping a mystic four-leaf clover that grants the holder limitless good luck to himself and the Leprechaun wants to take it back.

Martin goes on a school trip to a museum where there is an exhibition of pirates, and he decides to see where are the things of an old pirate that was told to have supernatural powers. Taking a medallion with him, Martin, or maybe "Captain Blood" now, he's gotten Java and his teacher under his spell and is out to find the treasure, the Red Rose Ruby that can raise the spirits of his crew.

A student's plant experiment for the Science Fair goes awry and the plant starts to eat the competition and anything that gets in his way.

Martin, Billy, and Java start their own band to attract the girls. But Martin finds out that his new electric guitar is possessed which transforms his girl fans into love monsters.

Martin, Billy, and Java start their own band (known as the Sophisticates) to attract the girls and their first gig is Diana's Modern Low Tea Society, who only members are girls. But when Martin's new electric guitar caused all the girls in the club to fall for him (Minus Diana) he must run from them as they are transform into love monsters, while at the same time running from some of the girls' boyfriends who want to hurt Martin.

M.O.M., Java, Billy, and Diana decide to take Martin to Terrorland, an amusement park for his one-year investigator reunion, but in this park the things come alive by an Egyptian spirit that thought a ride was the tomb he was guarding.

Things get more complicated during his visit as he also discovers that Jenni works at Terrorland and she insists that he doesn't tell anyone that he saw her working at Terrorland, but after saving her from a zombie she discovers Martin's secret identity as a secret agent for the centre & she instantly gets a crush on him wishing to become his girlfriend.

Jenni is seen lying down by the fountain and sees Martin stood alongside her dressed in a suit, she annoyingly asks Martin what stunt he is trying this time. He tells her that this is no stunt he was trying on her this time as he was being serious explaining why he was wearing a suit. Jenni still doesn't believe him saying that the only things he is serious about is comic books and pepperoni pizza, Martin then pulls out a ring box and asks Jenni if she will go on a date with him. Expecting to see something paranormal inside the ring box she is shocked to see that inside the ring box is a real diamond ring. She immediately accepts it and tells him that she will happily go out with him saying that he was finally acting like a normal guy instead of a freak interested in paranormal rubbish. The ring suddenly changes into a worm and Jenni is about to attack Martin, but he suddenly wakes up from what was actually a nightmare. "Note to self sushi before bed time equals nightmares". He then sees three people enter his room and before he can react he is thrown into a bag then dragged away before being thrown into the back of a van.

After capturing the scarab spirit and M.O.M plus Billy, Diana and Java are returned to normal. Martin tells M.O.M. that they need to get the artifact back to the real tomb where it belongs which M.O.M. says they will sort out immediately. Jenni now having a massive crush on Martin for being a secret agent asks Martin if she would go on a date with him, this being to Martin's shock aswell as Diana's annoyance as Jenni normally dislikes Martin. As they both walk away Jenni asks Martin to tell her all about his secret identity as she now wants to be his partner. With Martin begining his tale about starting as a center agent M.O.M., Billy, Java and Diana can only watch from a distance and to their annoyance that Martin is revealing their secret identity.

The following morning in a repeat of deja vu from his dream, Jenni is seen lying down besides the fountain as Martin walks up to her and presents her with a ring box. Inside the box is a paranormal ring which Jenni rejects in disgust, unknown to Martin that while his dream had come true for one day, the center had needed to erase Jenni's memories of the previous day.

Martin is reunited with his "first crush", Vivian Michelle, who embarrassed him during the grade school many times. Martin tries to avoid her, but when he finds out that Vivian has changed, he changes his mind about her. Diana suspects that Vivian is different due to her strange skin. Vivian is actually Venoso, a mutated chameleon-like monster who was the first monster Martin ever caught and also out for revenge with her cunning and sadistic nature.

Martin and Diana are stuck at school for Christmas until M.O.M. invites them to the Center's Christmas party. All goes well, until an evil and villainous elf named Jingle Jim, (Mig Elgnij) intends on ruining everyone's Christmas by twisting their Christmas wishes.

Diana's eager to get home before paranormal weirdness ruins another Christmas though Martin wouldn't mind a bit of weirdness. It looks like Java's going to be stuck alone in the empty school for Christmas when Martin and Diana get a call from their Dad. He's on an expedition to the North Pole and trapped by a blizzard so he won't be home for Christmas. Diana's sorry to hear that but gets much sorrier when Dad tells her that he and their mother think it would be best for them to stay in Torrington for X-mas (no explanation why their mother would rather spend Christmas alone rather than with Martin & Diana).

Java's happy for the company but Martin and Diana are gloomy about being the only teenagers left in the school. Then M.O.M. calls to invite them to attend the Center's Christmas Party (or else) which is a welcome distraction but Martin has to do some last minute Christmas shopping. Unfortunately the presents he gets are cursed by an evil elf who was kicked out of Santa's workshop and delights in ruining Christmas for others. Martin's gifts give the peace and quiet loving Diana huge ears that are very sensitive to noise, cause M.O.M. who hates Christmas music to sing everything she says as a Christmas carol, make the white Christmas loving Java melt snow and fulfill Billy's wish to spend more time with Martin by fusing them together.

To make matters worse after distributing 100 cursed gifts (which he's almost done) the elf will disappear at midnight for 100 years making the curses irreversible. Time is running out for Martin to undo the damage he's caused before it's too late and this becomes the worst Christmas ever.