Mark Grayson is a normal high school freshman with a normal part-time job whose father, Nolan Grayson, is an extraterrestrial of the planet Viltrum (with humanoid forms similar to Kryptonians) known as Omni-Man, the most powerful superhero on the planet. At age seventeen, Mark begins to display super powers as a result of his Viltrumite ancestry. According to Nolan, the Viltrumite race pioneers the entire cosmos on a mission of benevolence and enlightenment.
Initially the first three volumes focus on Mark as Invincible, who begins working as a superhero with his father acting as his mentor, and meeting other heroes (including Robot, Rex Splode, Dupli-Kate and Atom Eve). His exploits range from discovering that his physics teacher has been turning his students into human bombs, to foiling a plan by the Mauler Twins to make an army of robots. Meanwhile, Omni-Man kills the Guardians of the Globe in order to prepare Earth for the Viltrumite empire's impending invasion, leading Mark to battle his father.
Story arcs that follow this range from Mark traveling to alternate dimensions and battling villains like Angstrom Levy to facing off against Thragg, the emperor of the Viltrumite Empire, to determine the fate of Earth.
