The biggest question, of course, is what happened to Peter Bishop? At the end of Season Three, Peter stepped into the doomsday machine only to arrive in a destroyed New York City 15 years in the future. After some careful maneuvering, Peter used the time machine to end the destruction, but erased his own existence in the process. Promo photos for the new season show the cast, including Peter, walking in an unfamiliar setting, with a cloudy blue sky and a clear bubble-like dome behind them. Is it the future? Is Peter trapped here? How did the others get there? Or is it just a cool backdrop for a promo shot? Tune in to find out

Season Four of Fringe premieres tonight at 9 p.m. on Fox.