The Cat Who Wasn't There: Lillian Jackson Braun

In this Book Qwill goes with Polly and a group of locals to Scotland. Polly and the tour guide room together and Qwill's old love interest, Melinda Goodwinter is along and keeps propositing him. Melinda's father passed away and to the town's surprise, was in debt. Melinda wants to marry Qwill to have children and for his finances. The tour guide suddenly dies and Melinda claims it was her heart. The next day the bus driver, who was supposed to be a friend of the tour guide's also disappears with some of the luggage with a fortune in jewelry. Once back in the states Koko helps Qwill piece together the drama. Melinda and her brother had been living off their father for years and his death left them penniless. Melinda tried poisoning Polly with pills that looked like her vitamin C, only Polly's roommate took them. Melinda commits suicide at the end by driving her car into a wall. She left Qwill a note, but before he could read it, Koko chewed it up.