'Alcatraz' recap: The Future is Now
The team is alerted to his reappearance when a video of his bar killings goes viral. They track him down by interviewing his former neighbor Jack Sylvane (yay!), finding where he's buying his poisons and then to his freshly-abandoned makeshift lab. Eventually, they intercept him in the subway, where they foil his plan to gas a car full of men with phosgene.
In the flashbacks, Lucy tries to help Johnny. At first he's reticent, but she presses on. The girl that he's been talking up as his sweetheart was actually the girl who humiliated him in front of a gym full of boys. They pelted him with firecrackers, one of which blew off a testicle and made him kind of bitter about the scrotally complete.