In LOST, Season 1, ep. 6 - "The House of the Rising Sun" at about 20 minutes, when the Korean guy comes home with blood on the shirt, and the woman follows him into the bathroom. Before, it is crearly visible that his right sleeve has blood on it, but just between when she says "what were you doing? what happened?" and he responds "I was working." She then grabs him by the hand (the right hand) and blood is suddenly gone from the shirt!