[1] While studying the archaeological records of the now-destroyed planet Sarpeidon, a scholar aboard the USS Enterprise finds pictures of an ice-age cave painting that depicts a Vulcan face.

Due to a miscalculation, they find a young man of twenty-eight instead of a child, who tells them that his name is Zar and that his mother Zarabeth died in an accident many years before.

Zar returns to the Enterprise and passes as a distant relative of Spock, who oversees his education and attempts to train him in Vulcan telepathic techniques.

It is imperative to the security of the United Federation of Planets that the Romulans not discover the Guardian's powers; if they cannot be driven away, Gateway must be destroyed.

Zar volunteers to help Spock place the force field, because he can sense whether Romulans are present even though, due to the cloaking device, he cannot see them.

Once the Romulan threat is over, Zar decides to use the Guardian to return to Sarpeidon's past, but to a more settled location than the one he originally inhabited.

Crispin loved Roddenberry's optimism for the future and was inspired by the strong and capable Vulcans who nonetheless chose to embrace pacifism.