Victor (Bill Nighy) is a top professional killer who is about to retire and is experiencing a midlife crisis. He has been single since middle age and lives a monotonous and stereotyped life. His mother has been forcing him to find a woman to carry on the family line so as to "inherit the killer gene in the family blood". Once he was hired by the gangster Ferguson (Rupert Everett) to kill Rose (Emily Blunt), a professional liar who forged famous paintings. However, during the action, he developed an inexplicable feeling for the beautiful and passionate Rose. At the critical moment, he not only let her go but also began to protect her. During the escape, he met Tony (Rupert Grint), a young man working odd jobs in the parking lot. Tony mistakenly thought that Victor was a private detective and worshipped him as his apprentice. After Ferguson found that Victor had not completed the task, he sent the "second best" killer in the industry to continue to complete the task and also eliminated the "default" Victor and his apprentice. What kind of experience will develop between Victor, Rose and Tony, three people who have nothing to do with each other?