Author:	Fred Saberhagen
Copyright:	1967
Date Reviewed:	1/8/84
Rating:	5.0

Synopsis: The planet Sigrid is positioned near a section of warped space making time travel possible. The Berserkers, in an attempt to kill the human population of that planet, attack it through its past. Derron Odegard is assigned to fight the Berserkers, directly and indirectly in three different pasts. If the humans can beat the Berserkers three times, they can 'triangulate' their time coordinate and destroy hem.

Review: This book is essential a time travel story; and a mediocre one at that. The author uses time travel simply as a vehicle to tell a story rather than trying to explore the implications of it. The many time inaccuracies (e.g., events in the past will be seen in the future a few day later; time travel around one planet) soon get tiring. Other than this major flaw, the story is fairly interesting; though the two history lessons are too long.