Nick's nearest living relative is her cousin Charlie, who arranged for the remortgaging of End House to provide her with much needed funds. Nick's housekeeper is Ellen. Mr. and Mrs. Croft lease the lodge near End House. George Challenger likes Nick. Her two closest friends are an abused wife named Freddie, and Jim, an art dealer in love with Freddie.
If Nick were to die, Charlie would inherit end House and Freddie would get the rest of the estate. Poirot recommends that Nick not stay alone. She sends for her cousin Maggie. Nick hosts a party at End House inviting everyone but George. A renowned pilot named Michael Seaton has gone missing. k Guests speculate as to his fate. Maggie is discovered dead, wearing Maggie's shawl. Poirot launches an investigation.
To protect Nick, Poirot tells everyone she is staying in the hospital. IN the meantime, Michael is found dead and Nick confesses that they were secretly engaged. Michael, the sole inheritor of a wealthy estate, has indicated that it will go to his fiancee. Poirot finds love letters written by Michael but he does not find Michael's original will. Mr. Croft says he gave it to Charles who deceives receiving it. Nick receives a box of chocolates laced with cocaine delivered by Freddie allegedly sent by Poirot. She only eats one, avoiding disaster. Poirot suspects Freddie who is a cocaine addict.
Poirot stages Nick's death. He states that Nick's will awards all of the money to the Crofts who helped Nick's father in Australia. Everyone is surprised except the Crofts. It turned out they forged the will after they heard about Nick's death. Suddenly someone shoots at Freddie; it's her dying husband who has been begging her for money.
Poirot reveals the murderer as Nick. It turns out that Nick's cousin Maggie was engaged to Michael. Nick pretended that she was her cousin to inherit Michael's wealth. George used to supply cocaine to both Freddie and Nick. The latter used her supply to poison the chocolates. Nick is arrested but not before she takes Freddie's cocaine box as a souvenir. She takes a lethal dose of the drug to escape the gallows.
Peril at End House circa 1931 courtesy http://www.agathachristie.com/stories/peril-at-end-house.