It starts as an old story - Old seasoned civil engineer Joe Marshall does not like being gradually pushed aside by the younger upstart engineer, Adam Conrad, who Marshall considers an office dweller, lacking in field experience.
Into this tension comes two issues. First, a road needs to be built on some land that the engineering firm is developing, but it will need to go through the home of an older woman who holds the place dear and claims it will be torn down "over (her) dead body". Second, it appears somebody has been chiseling a few dollars here and a few there at the engineering firm. Marshall accuses his rival, Conrad, of being said embezzler.
When Conrad hears about these accusations, he goes out to the woman's cabin, where Marshall is determining how to move the cabin somewhere else - a compromise solution that the engineering firm has come to with the consent of the owner. He is hit on the head as he enters the dark house. But after he leaves, his head still hurting, the body of Joe Marshall is found, killed by a blow to the head with a crowbar. Conrad is arrested for the murder and Perry Mason is on the case.
This had a plot that left me wondering - How did Perry solve that one? Apparently, the writers realized there was a bit of a hole there too, so Perry explains his logic at the end in a conversation with Della and Paul.
It's interesting to look back on the relative innocence of 1964 in this episode, with the owner of the remote cabin, Marguerite Keith, allowing young couples to rent out her cabin for honeymoons. I think she was going for an "Enchanted Cottage" motif, but instead she got "The Telltale Heart", even in these less crime ridden times.