We already discussed that one may not leave his residence area on Shabbat and Festivals - about two thousand steps from his abode. It may be a city, a stand-alone house in a field, or just a personal space, four steps around himself if he happens to be outside in the open area. Thus, if he is alone in a Shabbat field, he may walk the four steps of personal space, plus a circle of two thousand amot (roughly, steps). This circle is called his "techum."
If gentiles removed him from his techum - he looses his residence area, and in the new place he can only walk four steps around but no more. The same holds true if he leaves his techum while being temporarily deranged. If they then returned him to his residence, he regains the complete techum, because he is not to be blamed or punished for what happened.
Tangentially, some things cause a person to go against his will and his Maker. Idolaters may force him to do wrong (like in the above example) and the pressure of poverty. Why do we need to know? - to pre-emptively pray to be spared. However, one who suffers from poverty and intestinal disorders in this world comes purified into the next one. Some also add here a bad wife.
Art: Thomas Benjamin Kennington - The Pinch of Poverty