 CONT: When they are on Teabings plane, Sophie goes back to Silas to  question him. She rips the duct tape off his mouth. Then Langdon  gets her to walk away. Later, Sophie, Langdon, and Teabing are  talking at the front of the plane, and Silas can be seen in the  background, with the duct tape back on. Neither Sophie nor Langdon  had replaced the duct tape prior to leaving Silas.