After being dosed with poison, Red must retrace his steps to discover which of his closest allies has betrayed him, while the task force races against the clock to find an antidote that will save him.

When an associate of the Nash Syndicate is murdered, Red sets Liz and the Task Force on the case in order to recover evidence crucial to bringing down Ian Garvey. Meanwhile, Aram considers a step forward in his relationship with Samar.