Spock begins acting strange - even violent - as, unknown to the rest of the crew, he enters the Vulcan mating phase that strikes adult male Vulcans every seven years. Kirk must divert the Enterprise from a tight schedule to return Spock to Vulcan so his mating ritual may be carried out. But on arriving, it is discovered that Spock must compete with a gladiator of his prospective mate's choice - and that turns out, on the spur of the moment, to be Kirk.
