The tenth series of Doctor Who continues this evening with new episode Extremis, 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.
Doctor Who airs tonight at 7:25PM on BBC One.
This year's run is Peter Capaldi's last as the Doctor, previously announcing he would be stepping down after this year's Christmas special.
Capaldi first stepped into the TARDIS in 2013, and will leave the iconic role in the 2017 Christmas special after three incredible series of the BBC's global hit sci-fi drama.
Peter Capaldi said ahead of the current series kicking off: "One of the greatest privileges of being Doctor Who is to see the world at its best.
"From our brilliant crew and creative team working for the best broadcaster on the planet, to the viewers and fans whose endless creativity, generosity and inclusiveness points to a brighter future ahead. I can’t thank everyone enough. It’s been cosmic."
Peter Capaldi's final series also marks writer and executive producer Steven Moffat's last.
He said: "Like Peter, I’m facing up to leaving the best job I’ll ever have, but knowing I do so in the company of the best, and kindest and cleverest of men, makes the saddest of endings a little sweeter. But hey, it’s a long way from over.
"Peters’ amazing, fiery, turbulent Doctor is still fighting the good fight, and his greatest adventures are yet to come. Monsters of the universe, be on your guard - Capaldi’s not done with you yet!”