On a flight from Los Angeles to Paris, a mad scientist on the run from the CIA is transporting a coffin containing the body of a colleague infected with a genetically modified virus. While the 747 crosses a violent thunderstorm, the instability of the aircraft allows the corpse to get out of its container.

A team of mutant superheroes fight for justice and human acceptance in the Marvel Comics universe.

Some of the Season 4 episodes were aired during Season 3 to compensate for episodes in that season being pushed back.