Leslie Williams (Lee Grant) is a very important lawyer. She is good at her work but her big break and her big money arrived when she started to work in the office of his husband Paul (Harlan Warde). She devises a complex plot, in which she kills her husband in order to get to his money and inherit his office, but makes-believe to everybody that it was a ransom. She is worried and calls the police because her husband has disappeared, and some hours afterwards she gets a voice on the phone asking for some ransom money.
Lt Frank Columbo (Peter Falk) is one of the police officers who dedicate themselves to solve this case, especially when things supposedly go awry when she tries to give the kidnappers the ransom money, after having travelled to the middle of the desert by helicopter. However, what really happened was that Leslie has exchanged two similar briefcases, and instead of the money -which she has kept in a , she put some cut outs from newspaper inside. On the meantime, Leslie has put the money on her locker. Everybody else, including Agent Carlson (Harold Gould) thinks that the kidnapping has failed, and soon the body of Paul Williams is found. When Columbo realises that there is something fishy on all the ordeal, he goes to open the lawyer's locker, but it's too late, as she has already taken the money home.
The widow Leslie thinks that she can fool everyone. Her main problem is her stepdaughter, Margaret Williams (Patricia Mattick). Leslie tries to reason with her. Margaret is back for the funeral from her Swidish boarding school. Margaret hates her stepmother, as she always believed to be a gold-digger. Leslie threatens to cut her out of her parents' estate money, and wonders aloud whether Margaret will be able to keep on buying her friends without her parents' money.
Columbo pesters Leslie about the late Williams' car, as he usually does with people he suspects to be guilty. Leslie tries to go on with all the cases of his late husband. Columbo, however, cannot pin the murder on Leslie. He eventually talks with Margaret, who explains why she has always hated her stepmother.
There is a moment in which Margaret haunts Leslie all over the Williams mansion. Finally,Leslie realises that her stepdaughter doesn't want to frighten or kill her, the teenager only wants to reach an agreement with her concerning the money. Margaret promises to leave to Sweden forever if Leslie gives her a lot of money- the money which Leslie has kept from the fake kidnapping.
Leslie and Margaret will meet at the airport. Margaret boards the plane right afterwards. Leslie breaths and is about to leave. However, whom non other than Columbo is waiting for her at the airport coffee shop? They talk over two bottles of root beer. Suddenly, somebody brings a box to their table. Columbo opens it, and the briefcase with the ransom money is there. Columbo explains: he couldn't devise any final proof of Leslie's guiltiness, so she asked for Margaret's help. Columbo realised that Leslie was conceited, greedy and selfish; so was so selfish that, in fact, she couldn't imagine anybody not being exactly like her -- that's why she didn't suspect Margaret at all. Leslie thought that she could buy Margaret's thrist of revenge, and her love for her father with money. Leslie's prints are all over the bills.
Leslie is taken away. Columbo is left with the bill, but he realises that he hasn't got any money of his own at the moment. He doesn't touch the ransom money, but makes the waitress go crazy and finally asks her to send the bill to his workplace.