Rufus Sewell Mark Easterbrook Actor Sean Pertwee Inspector Stanley Lejeune Actor Kaya Scodelario Hermia Easterbrook Actor Bertie Carvel Zachariah Osborne Actor Sheila Atim Thyrza Grey Actor Christopher Bianchi Rawle Actor Madeleine Bowyer Jessie Davis Actor Georgina Campbell Delphine Easterbrook Actor Kim Chapman Rita Actor Kathy Kiera Clarke Sybil Stamfordis Actor James Fleet Oscar Venables Actor Poppy Gilbert Thomasina Tuckerton Actor Nicky Goldie Mrs Coppins Actor Henry Lloyd-Hughes David Ardingly Actor Ben Nathan Doctor Actor Ellen Robertson Poppy Actor Martin Buchan Vicar Actor Claire Skinner Yvonne Tuckerton Actor Rita Tushingham Bella Actor Sarah Woodward Clemency Ardingly Actor Sarah Phelps Writer, Executive Producer Agatha Christie Writer Ado Yoshizaki Cassuto Producer Leonora Lonsdale Director Damien Timmer Executive Producer Helen Ziegler Executive Producer Tommy Bulfin Executive Producer Basi Akpabio Executive Producer James Prichard Executive Producer