The Sherlock star jumped at the chance to record a spoken-word piece, entitled Flat of Angels, for the band's compilation album Late Night Tales as he is a big fan of their music.
The story, written by the group's author pal Simon Cleary, details the aftermath of a house party in alternating voices.
Guitarist Edd Gibson tells Britain's Daily Star, "You don't consider there are people playing Sherlock Holmes who then remove their make-up to the sound of Friendly Fires - it was a giddy surprise.
"We got a friend to write a story for Benedict to read out on the album."
The collection, due out on Tuesday (05Nov12), also includes tracks by Cocteau Twins and SBTRKT.