Burke's Law - Season 2 Episode 32 : Who Killed the Card? 1966

The head of a greeting card firm was killed, but not by the arrow protruding from his body. It was slow, methodical arsenic poisoning. His flirtatious teenage assistant takes a shine to Burke, but he's afraid she may be the prime suspect. If not, there are several others to choose from: the victim's ambitious successor, the mousy psychologist and his domineering wife, or the jingle writer. Burke's intentions are misunderstood and he comes close to being a second victim. The series ends with the whole cast of regulars involved in a big musical production number (of dubious artistic merit).