We investigate one of the greatest mysteries in modern science: dark matter — the invisible substance that makes up about 85% of all matter in the universe. Even though it cannot be seen or touched, its existence is inferred through powerful observational evidence: the unexpected rotation of galaxies, gravitational lensing of distant light, and patterns in the Cosmic Microwave Background. The episode explores leading dark matter candidates, including WIMPs, axions, sterile neutrinos, and MACHOs, as well as alternative theories like modified gravity. We then examine global efforts to detect dark matter, from deep underground detectors and particle accelerators like the Large Hadron Collider to space telescopes searching for gamma-ray signatures. While the mystery remains unsolved, the search continues to redefine our understanding of the universe — reminding us that most of reality lies hidden in the dark.