Emma Thompson (“Cruella”) has joined the cast of BritBox’s upcoming Agatha Christie adaptation “Why Didn’t They Ask Evans?”

“Paddington 2’s” Jim Broadbent will also appear in the three-part series.

Thompson and Broadbent will play British aristocrats Lord and Lady Marcham. Lucy Boynton (“Bohemian Rhapsody”) plays their daughter, the daring Lady Frankie, who finds herself on a murder mystery adventure alongside Will Poulter (“The Revenant”) as Bobby Jones.

Hugh Laurie (“House”) is directing the show and will also star in the adaptation as Dr. James Nicholson, the creepy clinical director of a sanatorium.

Based on Christie’s 1934 mystery, “Why Didn’t They Ask Evans?” follows Bobby and Frankie as they investigate a suspicious death in their neighborhood and in attempting to solve the mystery, almost get bumped off themselves.

The scene is set when Bobby stumbles across a dying man and finds a mysterious photograph of a beautiful young woman in his pocket. He soon enlists Frankie in the caper, who purposely crashes her car in order to be cared for by the slightly strange Bassington-French family, whom she and Bobby suspect are involved. Soon, the bodies pile up.

Rounding out the cast are Maeve Dermody (“The Secret Garden”), Conleth Hill (“Game of Thrones”), Daniel Ings (“I Hate Suzie”) and Jonathan Jules (“Small Axe”).

Miles Jupp (“The Durrells”), Amy Nuttall (“Downton Abbey”), Alistair Petrie (“Rogue One: A Star Wars Story”) are also set to appear, alongside Paul Whitehouse (“The Personal History of David Copperfield”), Morwenna Banks (“Skins”) and Joshua James (“Black Mirror”).

The series is set to air on the streaming service in 2022.