Leonardo builds an underwater suit and travels through the sewers to enter the Vatican, where he meets the pope and the mysterious prisoner; Giuliano reveals the identity of Rome's spy.
Cast:
Tom Riley
Laura Haddock
Elliot Cowan
Lara Pulver
Blake Ritson
Gregg Chillin
Hera Hilmar
Eros Vlahos
James Faulkner
Tom Bateman
Alexander Siddig