Curtis Lyons

A teenager (Astro) whose brother was recently murdered is identified as the latest person of interest; Finch fears that his ex-partner's son is getting close to discovering the machine.

Stan pursues a lead that puts him on the trail to one of Gregory's crew members, closing the gap between him and Elizabeth, and reigniting some of the deepest conflicts between her and Philip.

With the arms control summit under way, a shocking revelation from Philip throws Elizabeth - and her work - into turmoil. Stan follows a dangerous hunch.

Frank goes on high alert when a threat to New York City may be imminent following a terrorist attack in the Middle East.