So this is the night called Ostara, a completely unique birth ritual aimed at keeping the ship's population at a certain number (600 by the way.) Basically, this is the night when everyone finds out if they're allowed to have a baby. Christa, meanwhile, hears someone laughing in the hall.
So, Stokes. He's been ejected from the ship and is now in holding. But as far as everyone on Ascension knows, he's dead. And that's not the only thing going wrong on Earth.