The teacher believes the roles have been assigned randomly and receives a 15 volt shock. The teacher is in the room in Yale with the experimenter and they can't see the learner.
It is absolutely essential that you should continue! The shocks don't cause any permanent tissue damage.
I can't stand the pain
Milgram thoroughly debriefs the participant at the end of the study. The participant was introduced to the learner and assured that they didn't receive any shocks. The results shocked Milgram as they predicted 3% would give the highest shock, but 65% gave all 450 volts. 74% of participants said they had learned something of personal importance and only one person expressed regret about taking part.