A Delicate Case

Up at Gumshoe Jack Lord's office, the phone rang. It was the police chief William Smart, Bill, that phoned and asked if Jack and Belle could take on another missing person case? I know they are not your favorite, but the daughter, Susan Wills, to a wealthy philanthropist, Allan Wills, did not come home last night, and the parents Allan and Ruth Wills were deeply worried. This is not like our daughter, explained Ruth Wills. Well, said Jack Lord. What do we know about her whereabouts from last night? Susan was out together with four friends, Three girls, and one boy. they are all old friends of Susan and have stayed here overnight several times. I am looking at the door all the time expecting her to come home, however, I know she is not with us any longer, Well answered Jack, I have what is known as, extrasensory perception, or ESP. If we can have Susan's friends here, I can hear if they are telling the truth or not. It was so decided that Jack would listen to the answers that Belle gave to the entire household and the four friends. It included kitchen staff, cleaning crew, and the garden staff. Altogether quite a few people. Entering the room sat up for the purpose, each one had to enter through one door, were asked if they had killed Susan, or knew of her whereabouts, then they had to depart through another door. The entire household staff except for Allan and Ruth Wills and James the butler had been cleared. Now whom of these three people were the murderer?