Yep! Perlie is as stupid as he appears.In a flashback, Negan and Simon confront the Croat over his brutal murder of a young girl. In the present, Maggie and Negan lead an attack on Madison Square Garden to rescue Hershel and kill the Croat. However, the Croat anticipates their actions, and he lays a trap, evacuating his people from the arena while letting in walkers and using the sound and light systems to lead them to the tribespeople. Overwhelmed and outnumbered, most of the tribespeople are killed with only Maggie, Amaia, Tommaso and Ginny managing to escape into the sewers. Negan confronts the Croat who joyfully greets him and tries to get Negan to join him, attempting to kill Perlie as a sign of good faith. Much to the Croat's shock, Negan saves the marshal's life and escapes with him. However, Perlie holds Negan at gunpoint, threatening him with summary execution for his crimes despite Negan having just saved his life.
It was a Trap!
Not sure about the chances of survival in the sewers. I think I'd take a chance trying to get from the auditorium to the control room.
Cliff-hanger ending!