Just to test the brilliance of Sherlock's mind, Dr. Watson makes five people stand in front of him. Out of the five, only one is the truth teller and the other four are togglers which means they may tell the truth or lie on being asked. But on being asked again, they will switch which means if they told a lie the first time, they will tell the truth on second question and vice versa.
Sherlock is challenged to ask only two questions to determine who the truth teller is. He can ask both the questions to the same person or ask two different people. How will he determine who is the truth teller?