Cora, one of the last Sentinels, remains the last line of defense against an unknown enemy laying siege to her planet. Together with a handful of allies, Cora must find a way to protect the one thing this enemy had come to destroy - the humans.
In a space-faring future, an alien war criminal seeks vengeance on humanity, and a celebrated-but-bumbling hero is forced back into action... whether he likes it or not.