Alerted by a friend to the discovery of a crashed spaceship, the Challengers investigate and find three alien creatures that had been held captive in that ship. The Challengers see if they have enough borrowed time to get the creatures back in their cages.; After hearing a television report about a burglar with the ability to walk through walls, the Challengers patrol the city with honorary member June Robbins accompanying them. They arrive too late to stop another robbery but pursue the thief, Anton Zammer, to his hideout, an abandoned laboratory owned by the late Prof. Macon, who left behind a number of inventions Zammer intends to use for his own gain. Zammer uses a shrinking ray to capture and cage the Challs, but June escapes the same fate, assisting the team in returning to their normal size and capturing Zammer.