Alfred Hitchcock mystery series,

An old trunk involves the three investigators with dangerous criminals seeking a cache of stolen money.

Hired to discover why a wild-animal farm's tame lion has become unpredictably nervous, three young detectives begin an investigation that uncovers a smuggling operation.

Three young sleuths uncover a mystery buried since World War II when they come to the aid of trouble-plagued environmentalist who is protesting the drilling of off-shore oil wells.

When three junior detectives search for a valuable old Spanish sword lost since the Mexican War, the headless statue of a horse yields a clue.

The Three Investigators search for a stolen statue only to find that it has mysteriously come to life.

The Three Investigators become entangled in the theft of a string of rare pearls and a fraudulent scheme involving family inheritance when they try to solve the mystery of a ghost's appearance in the old Green Mansion.