In the book The Egypt Game the climax occurs when the girl and her brother are trying to get through the gate to go to their clubhouse. As the girl goes through the fence and her brother is watching, she is grabbed from behind. Her brother is immobilized by the incident. The professor sees what is happening from his window and yells for help. The man lets go and runs.
The scene is tense with all of the action coming to a climax. Once the man drops the girl, she is alright. The police arrive and her little brother tells the police who he had seen grab his sister.
Actually April is not Marshalls sister. April was the one who is grabbed.