Colin begins to like Lindsey, though he is foiled by her boyfriend, Colin Lyford (he and Hassan call him TOC, "the other Colin"), whose father is under Lindsey's mother's employ. Colin is still chasing his eureka moment, finally finding it in the theorem he created called the "Theorem of Underlying Katherine Predictability". It determines the curve of any relationship based on several factors of the personalities of the two people in a relationship. His theorem eventually works for all but one of his past relationships with a Katherine—which the novel explores.