What If? Marvel Zombies - 10 Things You Need To Know

The zombie apocalypse began after an infected Sentry crash-landed in the heart of Manhattan and bit Colonel America. 24 hours later, the zombie outbreak had gone global and the world that the superheroes once knew was over.

Although The Sentry has been referenced as the Zombiverse's Patient Zero several times, there was no explanation who infected him. And when the origin of the virus was revealed in Marvel Zombies The Return, readers were... really confused.

Decades after the virus began, it had spread, not just to other universes, but to alternate timelines. When Zombie Hulk infected The Sentry during the World War Hulk timeline, Uatu the Watcher realised the zombies were screwing up the entire multiverse. Although he couldn't stop the virus, Uatu could contain it in a permanent time-travelling cycle called a Causality Loop.

When the Sentry lunged at Uatu, the Watcher sent him into the past of the zombie universe, making this Sentry the same one that initiated the zombie apocalypse in the first place. If that explanation is too hard to wrap your head around, the alternative explanation is - it's a comic book.