 Martin temporarily ages himself four hundred Martian years. He has been studying human old age, and figures one can only fully understand it by experiencing it. The one benefit however is that his mind is still as sharp as a tack, since Martian brains don t deteriorate with age. Martin decides that one of his acts as a senior on earth is to take a job as a warehouse night watchman since seniors don t want to be burden to their families. At work, Martin is interrupted by a couple of intruders, two elder spinster sisters, Tessie and Matilda Harvey. Their story: their estate, the possessions of which stored in the warehouse, is managed by Mr. Filbert. They want the proceeds of the estate to open their dream teahouse, however Mr. Filbert doesn t think it s a good idea. Just then, Mr. Filbert drops by the warehouse. He apparently is a thief of historically significant jewels, which he keeps for his own personal pleasure. One jewel, the Raja sapphire, he stores in one of the Harvey s covered chalices at the warehouse. After Filbert leaves, Martin allows the sisters to leave, but not before they pilfer the chalice with the sapphire, which they don t know is encased inside. The sisters eventually do find the sapphire and after hearing on a radio bulletin that it was stolen, bring it to Martin since they don t know what else to do. Martin devises a plan to ransom the sapphire back to Filbert, and plan to catch him red handed with the jewel when he checks to see if it s still in the chalice. They first need to slip the sapphire secretly back into his possession. The independent Harvey sisters try and help, but almost thwart Martin s plan by accidentally knocking him unconscious. Luckily, Martin regains consciousness just in time to carry out the plan to completion. But after all is said and done, Martin learns that old age is only a state on mind, and one can remain young by being contributing citizens to society, much like the Harvey sisters.