 Nick realizes that all of the 11 previous murders occurred on dates that are prime numbers, all of which are among the 12 prime numbers possible up to the number 31.Because 5 is the only one of the 12 prime numbers that has not been used, he knows that the next murder will take place the next night, the fifth of the month.Nick appears to have been proven wrong when a woman is strangled one day ahead of Nick's prediction, after which the killer leaps out the window to his death.