is sent to a Vedala asteroid on a mission. The Vedala are the oldest known space-faring race and have discovered a threat to the entire galaxy. They have sent for a team of specialists, including Kirk and Spock. The two officers beam down to the asteroid and find themselves in a clearing with four other aliens and a Vedala representative. It introduces the other aliens: Tchar, hereditary prince of the Skorr; then Sord, a large strong reptiloid Next is Em/3/Green, a coward, lockpick, and thief. Lara, a humanoid female, has a flawless direction sense. Spock has been chosen for his scientific expertise and Kirk for his leadership and adaptability. Tchar explains that his people were great warriors two centuries ago and threatened to overwhelm the galaxy. They became civilized because of Alar, their religious leader and their teacher. When he died, Alar's brain patterns were recorded in an indurite sculpture. Someone has stolen the sculpture and the Skorr are prepared to make war on every non-Skorr in the galaxy. Spock warns that within two years, the Skorr could breed an army of 200 billion warriors. The Skorr government has kept the theft secret and they must recover it before the Skorr discover it is gone and launch a holy war on the galaxy. The thief is unknown but the Vedala have found its location: a "mad" planet wracked by all matter of natural disasters. Three previous expeditions have failed and the Vedala can't survive on the planet. All six specialists agree and the Vedala teleports them to the planet.
The team finds an ATV waiting for them. Tchar is unable to sense the Soul but the ATV comes with a sensor tuned to indurite. Em/3/Green notes he can handle the ATV and turns on the sensor. However, the planet fluctuates and the sensor explodes. Lara gets a fix from the sensor and boasts that she can't lose the trace. Spock points out her abilities must be perfect or the Vedala wouldn't have chosen her. Tchar flies ahead and Spock checks the supplies. Lara hits on Kirk, noting she finds him attractive. Spock confirms there are weapons, and Kirk wonders why when the planet is uninhabited. Spock notes they are there, and there may be other things guarding the Soul of Alar.
The team proceeds across the planet, which goes from rain to blazing heat and volcanic eruptions in a matter of seconds. Tchar spots a structure up ahead and senses the Soul of Alar within. However, lava approaches their position. The ATV lacks sufficient speed but Kirk suggests they use the power pack for one burst of speed. Em/3/Green admits he can do it. Working with Spock, The little alien rewires the battery while Tchar provides an overhead view and informs the others where they need to create a temporary rock barricade to slow the lava. Kirk and Sord drop the boulders into place and Em/3/Green and Spock finish the rewiring. Lara provides coordinates to avoid the lava flow and they proceed at top speed just ahead of the lava. They manage to outrun it but they hit a rock and Spock is thrown out of the ATV. He tells them to leave but Kirk gets out and gets him back to the ATV. They come to a slope and the engine burns out, and they run the rest of the way. Spock chastises Kirk for stopping him to rescue him but Kirk notes it's his job to keep all of them alive.
The planet's weather changes to freezing temperatures and they proceed on foot over what is now an icescape. Tchar flies toward the structure but a crevasse opens beneath Em/3/Green. Working together, the others hold him long enough for Tchar to lift him to freedom. Em/3/Green is too tired to be afraid but Kirk orders Sord to carry the alien. Tchar goes ahead and they come to a forested area. Sord thinks he saw something but Spock notes there is no life on the planet. They approach the structure and Tchar flies ahead to examine the building. Kirk scouts ahead and Lara goes with him, insisting it's her job. Once they're gone, Spock asks Sord what he think he saw. Sord doesn't know and figures he's seeing things, but Spock insists there is no life on the planet per the Vedala. Sord isn't so sure that the Vedala know the planet as well as they claim.
Kirk and Lara find the structure temple and the huntress suggests they collect a few green memories, but Kirk notes that he has plenty. The others approach and Spock notes the structure is in the same shape as the Skorr's primitive temples. Tchar points out the entrance and Em/3/Green is confident he can pick the lock. He goes to work but informs them that they're booby-trapped and if he doesn't open them all in time, an explosion will seal the entrance. Flying creatures suddenly attack from above. Sord covers Em/3/Green while Tchar engages one in the air and the others open fire. The creatures explode... revealing they're mechanized sentinels. They're unable to fire at the one battling Tchar, which carries him over the top of the structure. They have no way to get to the roof of the building from the outside. Em/3/Green opens the door and they all insist on continuing. Inside they find the Soul of Alar, suspended halfway above the floor. The walls aren't climbable but there's a ledge leading up. The door seals behind them and there's no lock on the inside for Em/3/Green to open. Kirk isn't surprised, noting that something must have destroyed the three previous expeditions: insider sabotage. All of them but the large-sized Sord climb up onto the ledge and slowly inch their way toward the Soul. Spock notes the structure is flexible enough to withstand earthquakes. The Soul is in a force field and they can't get all the way to it. Suddenly an energy beam fires from above, cutting off the ledge behind them. Kirk knows who their attacker is: Tchar. Tchar drops down and explains that he wants to see his people restored to their rightful place as bloodthirsty warriors. As a gesture of respect, Tchar turns on a gravity neutralizer and gives them the chance to fight as Skorr. They can't use phasers and violates Tchar's "rules" since he controls the structure's phaser banks. Kirk and Spock, skilled in zero-g, go after Tchar and manage to grab him. Kirk hooks his foot on the Soul and calls for retrieval. Lara activates the retrieval device and the Vedala teleport them all back to the asteroid.
Back on the asteroid, the Vedala assures them that Tchar will be cured of his madness. However, there will be no rewards for the team since the theft and recovery of the Soul must be kept secret. Sord wonders if there'll be questions but the Vedala assures them there will be none, and that in time even there memories will fade. Lara expresses once last regret to Kirk and then they return to their ships. Back on board, Kirk and Spock discover that from the crew's perspective they've only been gone two minutes. Kirk understands and orders the ship to its next assignment.