Mark finds himself mingling with his older sister, travel agent Dora Sloan (played by Betty White) when she comes to town buying her own home, which has just been fumigated. However, she finds herself crashing at Mark's place longer than she expects (and he wants) when the body of Harvey Wardell, the real estate agent who sold her the place, is found stuffed in a closet, a victim of the gasses. Mark thus takes it upon himself to solve the mystery and get his sister out of his home and into hers.
Oh, and justice for the murdered victim, too. Obviously.
"Death by Extermination" displays symptoms of the following tropes:
- Asshole Victim: Harvey not only screwed people over with his real estate deals, he had a habit of sleeping with married women and sexually harassed at least one of his female employees.
- Body In A Bread Box: Harvey's body is found in a walk-in closet.
- A Deadly Affair: Harvey was killed by his co-worker Genevieve, one of the many women he was parking outside of his marriage.
- Domestic Abuse: Larry Macklin reacted to his wife trying to sleep with Harvey with a black eye.
- Everyone Has Standards: Larry Macklin may have hated Harvey and was willing to beat his wife for sleeping with the man, but he says he never would have given Genevieve the barbiturates if he knew she was going to use them to kill Harvey instead of her own sleeping troubles, and is willing to testify to avoid the chair for being an accessory to murder.
- Failed a Spot Check: The exterminator did check the house before fuming it, but not closely enough to find Harvey stuffed in a closet. To be fair, the house has been abandoned for a whole year, and it took two hours to set up the fumigation tent.
- If I Can't Have You…: Genevieve believed Harvey when he said she was now the only woman in his life, and killed him when she found out he was still sleeping around.
- My Hovercraft Is Full of Eels: A downplayed example towards the end. As Steve is leading Genevieve and Larry away, Dora jokes that Mark is so sweet, she may just want to live with him. Mark tells her "sobre mi cuerpo muerto", which when Steve asks what it mean, Dora says it translates to "over my body dead". The correct translation would be "sobre mi cadaver".
- Omniglot: Dora can speak multiple languages fluently, which for a travel agent is very helpful.
- Slipping a Mickey: Genevieve knocked Harvey out by slipping barbiturates into his coffee.
