There were two main storylines this week, one involving Sylar and Parkman, the other revolving around HRG and Samuel.
Sylar contacted Parkman and threatened to kill Janice if he didn’t go into his head and get rid of all his abilities. He buried Sylar’s abilities and then trapped him into a lonely existence.
Peter showed up and took Parkman’s abilities to read his mind. He found Sylar and tried to rescue him because his dream showed Sylar saving lives, not hurting people, but he ended up in the same nightmare as Sylar.