When he begins his investigation of the Clutter murders, Dewey forms two main theories about what happened. One is that only one killer was involved – somebody with a grudge against the Clutters. According to this scenario, this person would have forced Mr Clutter, with the aid of a shotgun, to help him tie up the family before shooting them one by one. However, the difficulty with this is that it seems very unlikely that a single individual, even with a shotgun, would have been able to overpower four people, particularly Mr Clutter and his son Kenyon.
Dewey therefore inclines towards a second scenario, in which the killer is assumed to have had an accomplice. However, Dewey finds this problematic as well:
Dewey … found it difficult to understand how two individuals could reach the same degree of rage, the kind of psychopathic rage it took to commit such a crime.
Dewey, then, can accept that maybe one person was deranged enough to perpetrate such a horrific crime, but finds it hard to believe that there could have been two such people. Of course, this second scenario turns out to be the correct one, although the personalities of the murderers are not quite what he originally envisages.