Leslie Williams (Lee Grant) is the main villainess from "Ransom for a Dead Man," the second of two pilot episodes of Columbo (airdate March 1, 1971). She is a successful attorney and the wife of fellow attorney Paul Williams, as well as the stepmother to Paul's daughter, Margaret Williams.
Leslie was actually Paul's second wife; his first wife passed away shortly before Paul and Leslie began their relationship. As revealed later in the episode, Leslie was controlling of Paul, and it showed when he turned down a high-level position to work with her in their firm. At some point, Paul began to regret his marriage to Leslie, voicing his feelings to Margaret (who despised Leslie) and revealing his plans to divorce her. Paul proposed a separation arrangement with Leslie, but in response to the offer, Leslie turned heel and planned to kill her husband, doing so for Paul's money and out of sheer anger towards him.
The beginning of the episode showed Leslie working on her villainous plan, which had her devising ransom notes and clipping a recording of Paul to create an alternate message of distress. Later on, Paul returned home and found Leslie seated and pointing a gun at him, with the villainess shooting and killing her husband. After the murder, the evil Leslie placed her husband's body in the trunk of the car and dumped it over a cliff, and once she returned home, she phoned a friend of hers and told her to remind her to mention "tennis" to her. Sure enough, that call came later, and Leslie used it to claim that kidnappers phoned her and stated that they had abducted Paul.
Columbo joined the kidnapping case, which had the "abductors" demanding a $300,000 ransom. Leslie apparently made the drop, only to steal the ransom for herself, and later on, Leslie feigned shock over the news that Paul's body had been found. Columbo had been suspicious of Leslie due to her many mannerisms, including not asking about Paul's well-being during the demand, and her fainting over the news about her husband's murder. His suspicions increased after Columbo went flying with Leslie, as he figured out--from Leslie's description of Paul--that Leslie considered her husband a bore. Margaret voiced her own suspicions to Columbo, and her discovery of Paul's car keys found in Leslie's room led to Margaret accusing her evil stepmother of murder.
Though Columbo lambasted Margaret for falsifying evidence, it was actually a ruse, as he had what he needed to catch Leslie. The episode's climax had Leslie confronted by an angry Margaret, who pointed a gun at her stepmother and fired blanks at her, threatening to shoot her. Leslie offered to pay Margaret's trust fund in exchange for her silence, with Margaret agreeing to accept. The pair went to the airport, where Leslie was revealed to have hidden the ransom money, with both of them going their separate ways after the payment. Columbo later appeared and revealed that Margaret's actions were part of a setup, while lambasting Leslie for believing that her stepdaughter could be bought. He also revealed the money inside the case, and after seeing it, Leslie realized that she had been foiled. The villainess commended Columbo on his intelligence, right before she was taken away and arrested.