Idol on stage. Monster off-stage. R&B superstar R. Kelly was a serial sex offender who secretly targeted underage victims for more than two decades. Experts pinpoint the tell-tale signs of a predator. Idol on stage. Monster off-stage. R&B superstar R. Kelly was a serial sex offender who secretly targeted underage victims for more than two decades. Experts pinpoint the tell-tale signs of a predator. Idol on stage. Monster off-stage. R&B superstar R. Kelly was a serial sex offender who secretly targeted underage victims for more than two decades. Experts pinpoint the tell-tale signs of a predator. Idol on stage. Monster off-stage. R&B superstar R. Kelly was a serial sex offender who secretly targeted underage victims for more than two decades. Experts pinpoint the tell-tale signs of a predator.