A little bit of concentration and a little of meditation. That's all it took for Stephen to be able to take control of Lisa's body. He figured it would be just as easy to get back. He hesitated at first. He actually enjoyed being in her body, but he ultimately decided he better get back to his own body. However, concentration proved to be difficult to come by. Lisa's attractive body was the first distraction. She just didn't seem to have the same zen he had, making it difficult as well. He still kept trying.