Written by Steven Moffat and directed by Daniel Nettheim.

In the Haereticum – the Vatican’s secret library of blasphemy – there is an ancient book known only as The Veritas. Throughout history, anyone who has ever read it has immediately taken their own life. Now a new translation is online, and the danger is spreading. The Vatican appeals to the Doctor. Will he read The Veritas? But can even the Doctor survive the ultimate truth?

The Doctor is played by Peter Capaldi, Bill by Pearl Mackie and Nardole by Matt Lucas. Michelle Gomez guest stars as Missy.