Star Trek: Spock's Brain

A woman from a strange alien ship transports to the Enterprise. She stuns everyone on the bridge with a device on her forearm and takes an interest in Spock. When Kirk and McCoy wake up, they discover that that the woman has taken Spock's brain! They rig up something to control his body but even a Vulcan can only survive a limited time without a brain, so they must track down the woman's ship and recover the missing organ.