Career U.N. bureaucrat Howard Silk discovers he has a doppelganger in parallel dimension who's about to turn his life upside down.
Prime's effort to stop the assassinations leads him to look to Howard and the killer's double for help.
As Emily Prime makes the crossing to uncover the truth about the assassinations, Prime looks to stay close to Howard as he fights to stop Baldwin's return to the Other Side.
After agreeing to trade places with Prime, Howard discovers some shocking differences in his life on the Other Side.
While posing as Prime gives Howard insight into life on the Other Side - and raises questions about his own - the search for a spy inside OI uncovers new details about the security breach.
As Baldwin confronts Clare with a demand to honour their deal, Prime's investigation into espionage produces an unexpected suspect inside OI.
Groomed from childhood to be a spy inside OI, Clare faces exposure at a crucial point in her mission.
As Howard and Emily Prime learn the truth about Indigo, Quayle struggles with the news that Clare is spying for the Other Side.
As the hunt for the spy forces Prime to go on the run, Howard learns the truth about his wife as the Other Side conspiracy to infiltrate OI unfolds.
As the rogue faction's attack on OI sparks a dangerous diplomatic stalemate, Howard tries to escape the Other Side and reunite with his ailing wife.