[Delvo]

When the Parkmans met and Matt seemed to feel something from Old Parkman's mind pushing back at him, I was reminded of him being the only person who could look back at Molly when she looked at him; it seemed like his power was reflecting other people's powers back at them. That would imply that he has no power over anybody else who doesn't have power of his/her own. But inducing nightmares is very different from reversing other people's powers, and he did it to Mohinder. So either he's got two separate and completely unrelated powers (the effect on others' powers and the nightmare thing), or there's some way to connect the two things as results of a single power... like making other people's minds reflect back in on themselves.