"Masquerade!"
The FF start repairs after Blastaar nearly destroyed the Baxter Building but something goes wrong when Herbie attacks Sue. Reed learns that Herbie was possessed by one of Nova's crew members, the living brain Dr. Sun. Now Dr. Sun tries to kill the FF as he downloads himself into the FF main computer. Reed manages to lock all the ports, trapping the evil Dr. Sun as Herbie sacrifices himself for the good of the team by blowing himself and the main computer up.