Michael Sheen and David Tennant have been cast in the lead roles in the Amazon series adaptation of Neil Gaiman and Terry Pratchett’s “Good Omens,” Variety has learned.

The show is set in 2018 on the brink of an apocalypse as humanity prepares for a final judgment. But Aziraphale, a somewhat fussy angel, and Crowley, a demon, aren’t enthusiastic about the end of the world, and can’t seem to find the Antichrist. Sheen will play the role of Aziraphale, while Tennant will play Crowley. It will consist of six one-hour episodes.

Amazon declined to comment.

Sheen recently starred in the Showtime drama “Masters of Sex,” which ended its run on the premium cabler in November after four seasons. He has primarily worked in film during his career, having starred in “Frost/Nixon,” “Passengers,” both “Underworld” and “Underworld: Rise of the Lycans,” and “The Twilight Saga: Breaking Dawn” among many others. He is repped by ICM, Sanders/Armstrong/Caserta Management, and the U.K.’s Roxane Vacca Management.

“I first read ‘Good Omens’ as a teenager and it’s been one of my favourite stories ever since,” Sheen said in a statement to Variety. “To be part of the team entrusted with bringing it alive on screen is a bit of a dream come true to be honest. To work alongside Neil, who I think is one of the greatest storytellers of all time, is incredibly exciting. And, just like the rest of the world, I’m a huge fan of David’s so I relish trying to save it with him.”

Tennant is well known for playing the title role in “Doctor Who” for three seasons and nine specials. Among his other notable roles, he played the villainous Kilgrave in Season 1 of the Marvel-Netflix series “Jessica Jones,” Alec Hardy in the critically-acclaimed series “Broadchurch,” and Barty Crouch Jr. in the film “Harry Potter and the Goblet of Fire.” He is repped by UTA and the U.K.’s Independent Talent Group.

“Good Omens” was Gaiman’s first novel, written in collaboration with Pratchett, who died in 2015. Terry Gilliam was attached at one point to direct a film adaptation. It is the latest Gaiman television project in recent years. Fox premiered “Lucifer,” inspired by the character created in Gaiman’s Vertigo comics series “The Sandman” and subsequent solo series, in 2015. Earlier this year, Starz debuted Season 1 of “American Gods,” based on Gaiman’s book of the same name.

“Good Omens” is co-produced by BBC Studios with Narrativia, the production company of Pratchett’s daughter Rhianna, and the Blank Corporation and in association with BBC Worldwide for Amazon Prime Video and the BBC. Gaiman and Chris Sussman are executive producing for BBC Studios, and Rob Wilkins and Rod Brown will executive produce for Narrativia. Gaiman adapted all six episodes of the series and will also serve as showrunner.

Following its exclusive launch on Amazon Prime Video, the series will also be broadcast on BBC in the U.K. BBC Worldwide has the second-run rights internationally.