turn in on oneself—have as little as possible to do with other people:
- She has become introverted, turned in on herself, and has broken off contact with the world that she no longer knows.
turn oneself in—give oneself to the police:
- It seems that Ford’s brother, Rod, had convinced him to turn himself in, although he did not actually realize what Ford had done.
Note: The expression does not correlate in meaning with the phrase turn in—(coll.) go to bed:
- After we had a late dinner, we decided to turn in for the night.