As Mal'akh's plan culminates, Peter and Langdon wrestle over the sacrifice needed to save Katherine.

Langdon, Katherine, Nuñez and Peter partner with Sato and the CIA to spring a trap for Mal'akh.

Katherine and Langdon persuade Isabel to protect herself. Peter reconnects with Leviathan members.

Mal'akh sheds light on Zach's final days in prison. Langdon and Katherine face their shared past.

Mal'akh pressures Langdon and Peter to decipher the clues. Katherine, Nuñez and Sato try to regroup.

Langdon must reunite with Katherine and team up with Sato while Nuñez follows a hunch.

Forced to split up, Langdon follows the next clue while Katherine joins Sato to find her father.

With the CIA on their trail, Robert and Katherine turn to Nuñez for help; Sato interrogates Bellamy.

Robert and Katherine get help from an old friend while trying to decipher the most recent clue.

Young professor Robert Langdon is pulled into a complex mystery when his mentor is kidnapped.