During the battle on Titan in Avengers: Infinity War, the key moment comes when Doctor Strange reluctantly hands Thanos the Time Stone in order to spare Tony Stark’s life. Many believe Stark’s survival will be key to defeating Thanos in Avengers 4. But he’s just one piece of the puzzle.

According to a new theory, Ant-Man getting stuck in the Quantum Realm is just as important, if not more so, to defeating Thanos in Avengers 4.

The theory argues that if Doctor Strange already knew Stark had to survive the battle on Titan, why would Strange let him come so close to death? The answer is timing.

Rather than hand over the Time Stone right away, Strange had to wait until Ant-Man was in the Quantum Realm, where the diminutive superhero eventually gets stranded after Thanos’ snap. With no way to get out, people believe Ant-Man will jump into one of the time vortexes Janet van Dyne warned him about and end up in the future.

This mixes with another theory that claims Ant-Man will seek out Tony Stark and the two will utilize B.A.R.F. to figure out how to best utilize the Quantum Realm and reverse the damage done by Thanos. It makes sense—Ant-Man getting stuck in the Quantum Realm was no coincidence.

Although Ant-Man didn’t appear in Avengers: Infinity War, a moment in that film will be crucial to how Avengers 4 unfolds. Don’t be surprised to see Ant-Man further explore the Quantum Realm in search of answers as to how to defeat Thanos.