The planet where Dr Thomas Leighton lives and where the Karidian Company performs Macbeth, drawing the Enterprise off course at the start of The Conscience of the King.
Planet Q is the setting for the opening of the Original Series episode The Conscience of the King. The research scientist Thomas Leighton lives there with his wife Martha, and he summons his old friend James Kirk by claiming to have discovered a new synthetic food, taking the Enterprise three light years off its course.
The real reason is a travelling theatre troupe performing Macbeth. Leighton, one of the few surviving eyewitnesses to the massacre on Tarsus IV, is sure that the leading actor Anton Karidian is the former governor Kodos.
Kirk is doubtful until Leighton is found murdered after a party at his home. He then arranges for the players to travel aboard the Enterprise so that he can settle the question himself.