In the episode, Picard is tortured by Gul Madred in a number of ways, including isolation, stripping him naked, starvation, and causing him intense physical pain, all ending in a sick game where Madred shows Picard four lights and threatens him with excruciating pain if he doesn’t agree with Madred saying there are actually five lights. In addition to working directly with Amnesty International on the episode, inviting them to Los Angeles to help with the torture scenes, Patrick Stewart also watched tapes that included statements from torture survivors and even a long interview with a torturer who shared his experiences hurting other people.
In addition to his rather uncomfortable research, Stewart also insisted on being completely nude during the scene where Picard is tortured by being stripped naked, because he wanted to fully honor the experiences of those who had endured similar torture in the real world. (Generally, nude scenes are done with some kind of skin-toned undergarment or even a little sock, but Stewart wanted to be as exposed as Picard.) Stewart’s experience researching and filming the torture scenes might have been pretty unpleasant, but it helped lead to one of the very best episodes of “The Next Generation.”