A colony in desperate need of perishable vaccines, whose delivery was delayed when Kirk kept the Enterprise at Argus X to hunt the vampire cloud.
Theta VII is a colony world mentioned in the Original Series episode Obsession.
The Enterprise is due to meet the USS Yorktown and collect vaccines for Theta VII, where they are badly needed and will not keep for long. Before the rendezvous a gaseous creature kills members of a landing party on Argus X.
Kirk recognises it as the entity that attacked the USS Farragut eleven years earlier, and insists on staying to destroy it. Spock and McCoy remind him of the people waiting on Theta VII and question his judgment. Only after the creature is destroyed with an antimatter charge on Tycho IV does the ship head for the Yorktown.