Sidney asks Clifford to act out parts of the second act including violent struggle, then reveals the struggle was to enable him to have evidence to show why he needed to kill Clifford and that he plans to burn any remnants of "Deathtrap".
Sidney asks Clifford to act out parts of the second act, which includes a violent struggle. Sidney reveals that the struggle was to produce evidence that he needed to kill Clifford and that he plans to burn the manuscript of "Deathtrap".