Yesterday's Son

Summary
From the back cover: The Romulans attack the planet Gateway, where Federation scientists are studying the Guardian of Forever - the mysterious portal to the past.

The Enterprise must protect the Guardian - or destroy it. But Spock has already used the portal to journey to the past. On the planet Sarpeidon, 5000 years ago, Spock knew a beautiful, primitive woman. Now he has gone to meet his son!

Information

 * In 1999, this novel was reprinted as the first novel in The Yesterday Saga mini-series, along with Time for Yesterday.