Markham sits on his United Airlines flight, going over some equations.
The plane flies through a diatom cloud, and the captain gets on the speaker to say he is increasing altitude for a better view.
Markham continues going over the new equations governing tachyons, trying for that simple law that leads to complex consequences.
A motion catches his eye. A man gets up and screams in pain before going into a seizure. Two stewards carry him past Markham.
The point that keeps bugging him is Peterson's suggestion: Did Renfrew need to send a message at all to make a paradox? And even so, how could you tell if a tachyon beam truly changed the universe if you're a part of said universe?
The plane suddenly crashes into a Maryland forest.
Right before he dies, though, Markham suddenly sees an answer.