Female crew members must take over the Enterprise when the men are incapacitated by a race of sirens.

The Enterprise finds a long-lost explorer.

The crew of the Enterprise races to find a way to stop a cloud from destroying inhabited planets.

Spock travels back in time to prevent his death as a young Vulcan.

In orbit around a dead star, the Enterprise comes across a huge starship inhabited by a parasitic life form that threatens the entire ship.