David Bowie was in desperate need of a break by the the time 2005 rolled around. He'd spent the previous couple of years on a grueling world tour that was cut short when he suffered a heart attack in Germany, which hit not long after a lightning technician fell to his death before a Miami concert and, in a significantly less serious incident, a fan struck him hard in the left eye with a lollipop onstage in Oslo.
Nobody saw much of Bowie in the months following the heart attack, but by the summer of 2005 fans started spotting him in the audience of New York club shows by TV on the Radio and other up-and-coming rock bands. He didn't walk out onto the stage himself until September 8, when he sang "Life on Mars" backed by a piano, and "Five Years" and "Wake Up" with Arcade Fire at a Fashion Rocks concert at New York's Radio City Music Hall. He looked oddly frail during "Life on Mars" and even seemed to be sporting a black eye, but he came alive during a transcendent "Wake Up."
One week later he joined Arcade Fire again when they played Central Park, and then the following year he made a surprise appearance at a David Gilmour concert in London and sang a brief set with Alicia Keys at a charity show in New York. He seemed healthy and happy, and fans were overjoyed when he announced plans for a giant outdoor comeback show in New York as part of the High Line Festival. But the show was quietly called off and he hasn't sang a note in public ever since.