The Door Through Space by Marion Zimmer Bradley

The Door Through Space is a science fiction novel by Marion Zimmer Bradley. Wolf is an ancient planet, old even when Earth was still host to neanderthals. Wolf is also deadly, orbiting a cold red sun. There is only one Terran agent that knows Wolf well enough to pass undetected, however he had undone his use many years ago.

This scarred, bitter and aging Terran may be the only person who can uncover the secret of the Door Through Space.