It’s one of the simplest music-video concepts ever: a closeup of elfin Irish singer Sinéad O’Connor, sporting a crew cut and a black turtleneck, singing directly to the camera. It’s also the most heartbreaking. Written by Prince, the song is a lover’s lament. As such, the look on O’Connor’s face pinballs between nostalgia, anger and sadness, a temporary schizophrenia familiar to anyone who has ever experienced a significant breakup. Near the end, when O’Connor sings, “All the flowers that you planted, mama/ in the backyard/ all died when you went away,” two tears roll down her cheeks the result, said O’Connor later, of her tempestuous relationship with her own mother. (When Prince sings the song, he replaces “mama” with “baby.”) You’re a robot if you don’t follow suit. It’s raw and intimate and unforgettable.