What is the main conflict in Hell House by Richard Matheson?

Hell House by Richard Matheson is a story that takes four very different people into a house that has a life of it's own. After sitting empty and boarded up by the owners for thirty years, Rolf Rudolph Deutsch wants a small group of hand selected experts from several unique fields of study to go into the house and stay for one week. With the promise of great renumeration, all he asks in return is that they answer definitively the one question he has: Is there life after death?