Hello! I recently divorced my husband. My son is 14; a year ago he met…

Hello! I recently divorced my husband. My son is 14; a year ago he met a guy who is 21. Now my son has started drinking a lot; every day he doesn't come home before midnight — in fact he's being dragged in by his 21-year-old friend. The friend says not to scold him, claiming he's going through a difficult period in his life. Should I listen to his friend, or is it better that I take drastic measures myself?