OTTAWA -- The Pittsburgh Penguins flipped a switch and dimmed the lights on the Ottawa Senators.
Six unanswered goals in the final two periods Wednesday night lifted the Penguins to a 7-3 victory over the Senators, stunning 20,500 fans at Scotiabank Place in the process.
The Penguins now lead the best-of-seven Eastern Conference semifinal series 3-1. Game 5 is Friday in Pittsburgh.
James Neal and Jarome Iginla led the way for the Penguins with two goals each. Chris Kunitz, Pascal Dupuis and Sidney Crosby had the others.
Milan Michalek, Kyle Turris and Daniel Alfredsson replied for Ottawa.
Senators goalie Craig Anderson, who was brilliant in the first period, was pulled in the third after giving up a sixth goal on the 38th shot he faced. His replacement, Robin Lehner, stopped three of four shots.
Tomas Vokoun made 30 saves in the Pittsburgh net.
The Senators were up 2-1 after the first but things changed quickly after the intermission. Goals 40 seconds apart by Kunitz and Iginla had the visitors ahead by the 1:48 mark of the second period.
The Penguins pushed hard but couldn't get more until the third, when Neal scored on the power play at the 1:59 mark. Dupuis followed with a short-handed goal at 8:08, and then Crosby broke in to increase the lead 29 seconds later.
Iginla picked up his second, again with the Penguins on the power play, before Alfredsson snapped the run with a goal at the 14:44 mark and the Senators having a man advantage.
Alfredsson's goal represented his 100th career playoff point.
After Michalek set up Alfredsson for the dramatic short-handed goal that sent Game 3 into overtime, Alfredsson returned the favor with a neat pass in the defensive zone to spring Michalek for a breakaway -- and Wednesday's first goal -- with the Senators short-handed.
Anderson, who was victimized by Crosby for three goals in Game 2, made three huge stops off Crosby by the 11-minute mark of the first period in Game 4.
NOTES: Trade deadline acquisition Brenden Morrow was out of the Penguins' lineup as coach Dan Bylsma replaced him and Tanner Glass with two other forwards, Jussi Jokinen and Beau Bennett ... The Senators inserted 21-year old winger Mark Stone into the lineup for the first time in the playoffs and put him on a line with Jason Spezza. Stone, a scoring star as a junior, made his NHL debut in Game 5 of last spring's opening-round series against the New York Rangers and set up Spezza for the winning goal. He had played four NHL games since, at the start of this season, and was sent to the minors after producing no points. ... To make room for Stone, Senators coach Paul MacLean sat down Cory Conacher.