A big part of what makes Ant-Man so successful is how lighthearted the movie is. There are some dramatic beats, and, yes, the entire world is at stake. But thanks to some sharp writing and “everyman” acting by Paul Rudd, the movie has undeniable charm. That’s no more evident than in the movie’s ending.

Some spoilers ahead.

At the conclusion of Ant-Man, director Peyton Reed leaves the universe wide-open, showing Martin Donovan’s character, Mitchell Carson, escaping with some Cross Particles. In early drafts of the movie, however, it actually ended differently.

“At the end of the movie [Carson] gets away and has these Cross Particles, and there was a sequence where Ant-Man has an encounter with him,” Reed explained. “But then for a couple reasons, it felt like maybe we should leave those particles out there. In that original thing, [Ant-Man] took Martin Donovan out and got the particles.”

In Ant-Man, Carson’s main objective is to purchase the Yellowjackets suit, but ultimately fails. Instead he gets something even better, escaping with the Cross Particles without interference. Allowing Carson to escape with the technology leaves the story arc open to future appearances in the MCU. Now the question is when?

On the one hand, it would have been great to see Ant-Man confront Carson about the particles. However, allowing him to escape builds tension and leaves audiences wondering how Carson and the particles will factor into future films (if at all). Carson was a big part of S.H.I.E.L.D. and undercover Hydra agent, making him a huge threat. It’s very possible he’ll figure out how to reverse-engineer the particles and create new technology of his own.

When we’ll see Carson again remains to be seen. Marvel Studios hasn’t announced any plans for an Ant-Man sequel, though the superhero has already been confirmed for Captain America: Civil War. Perhaps Cap’s next adventure will allude to Carson for an appearance down the road.