The new episode of Jonathan Creek will air on Monday 1st April at 8.30pm, the BBC has confirmed.
The Clue Of The Savant's Thumb stars Alan Davies as Creek, who is called upon by returning Sheridan Smith as Joey Ross to help investigate the disappearance of a dead body from a locked study - which turns out to be the first in a chain of dark mysteries. Also making a return appearance is Rik Mayall as Detective Inspector Gideon Pryke.
The feature-length episode guest-stars Joanna Lumley as Rosalind Tartikoff, Nigel Planer as Franklin Tartikoff, Hasina Haque as Fariba Tartikoff, Michael Lumsden as local doctor and family confidant Peter Churchill, Sarah Alexander as media executive Polly, the new love of Creek's life, and Mark Frost as local farm worker Brad.
Also featuring in the episode are James Buller as Det Sgt Cudlipp, Sharlene Whyte as Det Con Atkins, Robert Styles as Jack, Louise Yates as Davina, Anna Burnett as the young Rosalind, Phoebe Jones as Natalie, Abigail McKern as Beth, Lydia Gerrard as the young Beth, Lucie Wolfman as Grace, Angelica Jopling as Kate, Mairead Conneely as Sister Cunegonde, and Samantha Coughlan as a receptionist.
As previously reported, the BBC One special, which has been written and directed by David Renwick, will be followed next year by a mini-series of three episodes.