Promise Me You Will Be a Dolphin
(Prométeme que serás delfín)

A school teacher is murdered in her classroom. Some of her students, childhood friends, try to avoid the catastrophe, and decide to investigate who the culprit is. Who would want to see Adela dead? The list is long but another terrible event shortens it drastically. In their intent to find the culprit, the girls will find out something they will wish they had never learned.