 A mysterious wave is headed toward Enterprise. An alien shuttle warns the crew that the radiation will kill them and seeks shelter aboard ship. With only hours to prepare, ship s control is rerouted and Enterprise personnel take refuge in the highly-insulated, close-quartered catwalk. Soon it is discovered that the alien passengers are immune to the radiation and lied their way into hiding on Enterprise, which has been boarded and commandeered by aliens who assumed it to be abandoned.