The Impossible Fortune by Richard Osman

Joyce's daughter, Joanna, is getting married. At the wedding reception, Nick, the best man, confides to Elizabeth that someone tried to kill him. He then disappears and his business partner Holly is murdered. The Thursday Murder Club members (Elizabeth, Joyce, Ron and Ibrahim) find themselves deep in a murder investigation that's related to a large amount of bitcoin along with a code to crack. Ron, though, is distracted by a feeling that all is not right with his children. Another enjoyable jaunt with the quartet and their circle of friends and family.