At Vulcan, Spock invites Kirk and McCoy to accompany him to the wedding ceremony. He explains that Vulcans are bonded as children so as to fulfill the "pon farr" commitment, and that T'Pring is to be his mate. T'Pring arrives with Stonn, a pureblood Vulcan, whom she prefers to Spock. T'Pau, a matriarch renowned as the only person ever to refuse a seat on the Federation Council, prepares to conduct the ceremony. However, T'Pring demands the "kal-if-fee", a physical challenge between Spock and a champion she selects. To everyone's surprise, she chooses Kirk instead of Stonn. Spock begs T'Pau to forbid it as Kirk is unaware of the implications, but T'Pau leaves the decision to Kirk; another champion will be selected if he refuses. Kirk accepts the challenge, only to learn that it is "to the death."