Evil Under the Sun (S08E01)

After collapsing during dinner, Poirot is banished to the resort island of Sandy Covc for a two-week recuperative stay. Subject to a taxing (and decidedly undignified) regimen of diet and exercise, he is distracted from his plight by growing suspicions that death awaits one of his fellow guests. When the body of Atlena Stew is discovered on the beach it is up to Poirot to determine who killed her. (official distributor synopsis)