Marshall mysteriously becomes invisible when he gets angry. He uses his new ability to follow Vaughn. Vaughn has been asked by his father Victor to steal Josie's journal to find out what she knows about black holes.
After Lucas is bitten by a mayfly nymph, he gets his wish and becomes an adult. However, due to the short lifespan of the mayfly, he keeps getting older and eventually turns into an 80-year-old man.
Josie and Vaughn are sent back in time to 1977. While there, they accidentally interfere with Vaughn's parents' first meeting, creating an alternative timeline in which he was never born.