Nomad

Gabe Fuentes has become Earth's ambassador, but he is not on Earth nor on the moon. He is traveling deep into space with the alien ambassador Kaen, who looks completely human, as well as with Nadia, the human ambassador from forty years ago who hasn't seemed to have aged at all. Nadia has spent decades studying the Outlast, an evil alien species determined to wipe out all civilization other than their own. If the three ambassadors cannot work together quickly, then Earth's fate and the Outlast's victory seem certain.