Taylor Swift was set to perform a series of shows in Vienna, Austria, late this week and into the weekend. But authorities canceled the shows after learning of an alleged ISIS plot to attack the music venues when crowds gathered for this stop on the much-hyped Eras Tour. Host Marco Werman speaks with Colin P. Clarke, director of research at the Soufan Group, to get the known details of the alleged plot, and to talk about music shows as targets of terror attacks.