With time travel expected to play a major role in Avengers 4, many people have wondered how the Avengers will acquire the Soul Stone. In Avengers: Infinity War, Thanos acquired the stone by sacrificing his daughter Gamora, the only person he ever loved. We’ll apparently see a sacrifice of similar magnitude when the next Avengers is released.

According to a new theory, Tony Stark will be the one to make the sacrifice—but it won’t be Pepper Potts. Instead, Reddit user SFMarch07 believes Tony will sacrifice his parents.

SFMarch07 explains:

Instead of sacrificing Peppe Potts, what if Tony instead has to go back in time to 1991 and infiltrate Hydra or seek out the Winter Soldier, and order the hit on his parents himself, sacrificing the thing he loves most, to enable him to get the Soul stone to fight against Thanos, knowing all the while what it will cause in the future and all the anguish it will personally cause him along with the events of Civil War, breaking up the Avengers, and everything that happens after that.

Tony has made sacrifices before, but each time it’s been his own life on the line, like when he carried a nuke through a wormhole to save New York City. Seeing Tony sacrifice that which he loves the most would be downright heartbreaking.

“It would be the hardest decision that any character has had to make in the entire MCU, and a decision that only Tony Stark himself could make, a burden that only he could bear, truly exemplifying him as ‘Iron’ Man,” according to SFMarch07.

We’ll find out how the Avengers acquire the Soul Stone when Avengers 4 hits theaters on May 3, 2019.