What are the motifs in I Know What You Did Last Summer by Lois Duncan?

Friendship or peer pressure are recurring ideas. The line between friendship and peer pressure gets blurred in I Know What You Did Last Summer. The relationships between these four young people starts out looking like true friendships. Two couples approximately the same ages; they go out together; they laugh and have fun together; they have similar interests. It is obvious, however that their friendship cannot survive the death of a child and the secret-keeping of the incident. Their friendship as a group dissolves as does the dating relationship between Ray and Julie.

The differences in personality and person