A mysterious killer is on the lose.

In the mountains north of Chiang Rai an animistic hill tribe follows their ancient beliefs. One such belief is that a widow known as a "Mida" must be appointed to teach men how to have sex before they marry so that they can have lots of children. This is a great honor for anyone that gets this position. One day some young pimps from Bangkok show up with the intention of convincing the local girls to go to work in brothels down there. They employ two locals to help them and pay them with things like tape recorders, watches and clothing. Once they leave the two who got the tape recorders etc. find out they cannot buy batteries up there, have no electricity and realize they have been cheated. The local people then begin to hate outsiders. Another Bangkok man comes up and at first they think he is just another pimp but find out he is a volunteer teacher. What fate awaits him, "Ah Por" and the girls who decided not to go?