The Adventures of Sam Spade – The Stopped Watch Caper. ep146, 490410

A security guard dressed in a dark uniform is reaching for his sidearm, which is holstered on his right hip. He stands in front of a brick wall, with his left hand resting on his belt. His facial expression suggests a state of high alertness and readiness to act in case of any threat or danger.
Security Guard Drawing his Weapon --- Image by © Royalty-Free/Corbis "Used with permission from Microsoft."

Sam has a substitute secretary, Effie’s little sister, Buffy. Clued into a weird family, in a house in the swamps, Sam is intrigued enough to see it for himself. In the humid, green foliage, Sam meets the first odd relative, and gets a lesson on the deadly plants surrounding the place. Boris the butler shows him in to the eccentric aunt. A broken watch is the clue, but did it stop because it was tampered with, or some other reason? Suddenly Mrs. Raven falls ill. Was she poisoned?

The doctor is on hand and confirms the aunt died of poisoning, and now Ralph is showing symptoms of it. Strange events continue, with disappearing and reappearing watches. Sam uncovers the possibility of radioactive elements on the land.

Crazy people go even more wacko when secrets are revealed.
The secret of the medicine, poison, and stopped watches are explained when Sam files his final report with Buffy.

PS: Not sure why they switched the character from Effie to Buffy. She is still voiced by Lurene Tuttle, so it wasn’t like she had a day off… just another character to play. Besides, in the ageless world of Sam Spade, Effie is supposed to be 19 years old. How young is this sister supposed to be, I wonder.