Well, he can scry the past, beginning with a given place or person, and "traveling" to different places and times and people from there. The closer a moment is to the present, the less reliable the scrying, I figure within an hour or so is not visible to him. With the scientist there in the room with him, he could potentially look back at anything the scientist had done, experienced up to within an hour of the present. He can't read past thoughts or anything. 
When "traveling" past moments, personal connections are the easiest fastest way to get to different places/times/people. Any other connections takes significantly more time to navigate.
Assuming of course that sounds reasonable.