When a group of religious extremists called the Redeemers target the planet Haresh for purification, Captain Calhoun of the Starship USS Excalibur is outraged. He orders the ship to Haresh to intervene... but on the way there, an emergency rescue on another planet slows the Excalibur down, so that it arrives too late. Haresh is already a dead planet. Calhoun doesn''t take defeat lightly, though... so he tries a risky scheme to travel back in time, arriving at Haresh early enough to save the populace from the Redeemers. This maneuver isn''t universally popular, though, either with his crew or the Federation timeship USS Relativity. That ship''s Captain Braxton is prepared to use force against the Starship USS Excalibur, in the pursuit of his mission to keep the timeline intact. With the Federation on one side and the Redeemers on the other, Calhoun is a man in the crossfire. And there''s no easy way out..