When Harry Barton is sent to live with his elderly great aunts, he discovers that they rob banks in order to give money to the poor.
Harry is in for shock when he discovers that Lavinia McScrew is teaching at his new school.
When Harry is caught and sent to an institution, it's down to the wrinklies to rescue him.
The Wrinklies' plan to raid Percy's house is foiled, but after celebrating Harry's birthday they are ready to plan another robbery.