The evil Victoria Dawn
Victoria Dawn (Patrice Wymore; 1926-2014) was the main villainess from "The Case of the Murderous Mermaid," episode 8.23 of Perry Mason (airdate March 18, 1965). She was a former swim champion who operated a swimming school.
Victoria gained fame 10 years prior for swimming from Catalina to the coast, and she was planning the stunt again in the episode's events; however, aspiring actress/stuntwoman Reggie Lansfield was enlisted to pose as Victoria and perform half of the stunt to gain fame for Victoria. Victoria was first shown with her husband Doug Hamilton, her sister Lillian Keely, and Dr. George Deviln watching Reggie take laps in Victoria's pool, with Victoria approving of her performance.
Later on, Reggie catches Doug and Lillian embracing in a romantic manner (confirming Victoria's belief that they were having an affair) and overheard them talking about being rid of Victoria after the stunt, leading Reggie to believe that the illicit couple was using the stunt to try to kill Victoria. However, Victoria responded to Reggie's warnings by revealing that Doug was divorcing her, and afterwards, Reggie performed her portion of the stunt, but became exhausted--even after Charlie Shaw, who operated the boat that accompanied Reggie, gave her broth to replenish her. The boat later explodes, nearly killing Charlie as he was trying to get Reggie aboard, and afterwards, Reggie visits Victoria to inform her about the stunt, only to find her deceased, having been killed.
Reggie was the primary suspect, but the trial and the episode's progression provided surprising reveals regarding Victoria. As uncovered by Charlie during his testimony, Victoria turned heel and planned to kill Reggie, with the broth being the first attempt, as the villainess drugged the broth so Reggie could become incapacitated and drown during the stunt. Regarding a second attempt, the evil Victoria planted dynamite on Charlie's boat, serving as a backup plan in case the drugged broth didn't affect Reggie. Regarding a motive, Doug revealed that Victoria had embezzled $250,000 from her business, and knowing that Reggie was posing as Victoria (as well as Victoria herself being insured), the villainess planned to kill her and disappear, with the insurance money making up for the embezzlement.
Victoria was planning to run off to South America with Deviln, as they were illicit lovers. However, Victoria was killed by Charlie, who had feelings for Victoria and was angry that she didn't reciprocate, leading to an angry Charlie bludgeoning her to death with a bookend.