Henry Carter Hull

Vicious traps and threats beset Frank, Joe, and Chet as they search for two stolen, famous paintings in an old fort said to be inhabited by a ghost. One of the paintings is a clue to the hiding place of a chain of gold.

While searching for the guard end of a broken saber that will solve one mystery, the Hardy brothers become involved with a gang of bank robbers.

Suspecting that their friend has been swindled, the Hardy brothers investigate and find themselves on the trail of a much larger criminal operation.

The Hardy boys and two friends take a camping trip to the Rocky Mountains in an attempt to locate a gang of credit-card counterfeiters.

In trying to trace a missing will, detectives Frank and Joe Hardy trap a dangerous criminal who is willing to risk all--including murder--for money.

Relates seven cases in which the Hardy brothers use police technology to track down criminals. Details of these techniques and precedures are given in the last five chapters.

Hired to locate an old Spanish cannon, the Hardy brothers uncover an even greater treasure after perilous underwater adventures.

The Hardy brothers' visiting Greek pen pal enlists their help in searching for a priceless ancient Greek helmet loaned to and lost by a Hollywood movie company years before.

The search for missing gold takes the Hardy boys to the Yucatán Peninsula where they uncover a second mystery.

Two teenage sleuths help their detective father search for a famous rocket scientist whose disappearance endangers the launching of the Firebird Rocket.