Lately, Spock’s behavior has been increasingly and unprecedentedly erratic. When McCoy finds it to be a growing medical risk, Kirk drags the truth out of him: it is the ‘blood fever’, the one time in a Vulcan’s life he regresses to a primitive, hormonal state of mind, setting out to mate for life. He is granted the first request for shore-leave in his entire career to go to Vulcan, asking Kirk and McCoy to join him in his equivalent of a marriage ceremony with his since-age-seven arranged fiancée, T’Pring. But, once on Vulcan, T’Pring halts the matrimony by calling the ancient challenge, whereby a champion of her choice will fight Spock for her. Surprising all, she selects Jim Kirk. He accepts after due consideration only to find, when the first of two dueling weapons are handed out, that the fight is to the death – too late to decline in front of T’Pau, the presiding top official for Spock’s family and the most powerful of all Vulcan dignitaries.