The CBI team is called to investigate the death of the wealthy new owner of the old Beckworth Mansion; where his murdered body was found. The man and his wife bought the Mansion with the hopes of fixing it up, and the sentimental former owner developed a grudge. The local deputy sheriff, and other witnesses, believe that Walter Beckworth's ghost haunts the mansion and killed the new owner, so the investigation is accompanied by a discussion about the existence of ghosts. Jane discovers that the ghost was actually an illusion created by a system Beckworth built into the house to entertain his guests and also points out that the house is full of secret passages that the killer could have used. The CBI team and others, headed by Jane, then tries to find a treasure supposedly hidden in the house, and disovers a riddle. The killer; the former owner's jealous nephew, is tricked into sneaking undetected into the mansion again in an attempt to locate the treasure and he is apprehended by the CBI upon arrival. Patrick reveals he wrote the riddle himself. Also, Van Pelt and Rigsby become closer, and finally express their feelings for each other.