Yesterday, Upon the Stair

Overview

When Hunter helps with the exchange of a U.S.-held Communist spy for a Communist-held American spy—who happens also to be his favorite instructor in spycraft—persons unknown intervene in the exchange and kidnap both of the spies being exchanged. Hunter and Marty are assigned to find the missing American spy, and Hunter begins to suspect that a traitor in his own agency is responsible for the kidnapping.