McAmmond tossed the puck out from behind the red line, redirecting it off the skate of Ducks defenceman Chris Pronger and into the net past goalie Jean-Sebastien Giguere at 18:34. The goal gave the Sens their first lead of the game after Ottawa rallied from three separate one-goal deficits.
Alfredsson tied it 3-3 with his first goal of the series at 16:14 of the period, redirecting the puck past Ducks netminder Jean-Sebastien Giguere with his left skate. The goal was initially waved off, but was later allowed after a lengthy video review.
While the Senators turned up the physical play in the second, the Ducks were the more dominant offensive team in the the first half of the period. Corey Perry put Anaheim up 2-1 at 5:20, walking out untouched from the right corner and sliding a shot between the legs of Senators netminder Ray Emery.
Ottawa's Mike Fisher responded 27 seconds later, tipping an Anton Volchenkov point shot past a screened Giguere.
With the Scotiabank Place crowd of about 20,000 still buzzing, Ryan Getzlaf gave the Ducks their third lead of the game at 7:38. Dustin Penner's shot from the left faceoff circle handuffed Emery, allowing a charging Getzlaf to slap in the rebound.
Anaheim forward Andy McDonald and Ottawa grinder Chris Neil traded goals in the first, with Neil's goal ending Ottawa's drought at 111 minutes, 34 seconds dating back to the second period of Game 1.
The electric crowd blew the roof off Scotiabank Place as the Senators hit the ice, celebrating Ottawa's first Stanley Cup game in 80 years. The majority of the fans were clad in red, and all were given red pompons to shake.
The Ducks received their own emotional boost with the return of forward Chris Kunitz, who was added to the lineup for Game 3. Kunitz, who had 25 goals and 60 points in the regular season, broke his hand in Game 1 of the Western Conference final against Detroit and wasn't expected to return for another week.
Kunitz was paired with regular linemates McDonald and Teemu Selanne, and the feisty line immediately drew the first penalty of the game. Senators defenceman Wade Redden knocked Kunitz to the ice as the Ducks winger charged towards the net.
McDonald made the Sens pay on the ensuing power play, converting a Selanne pass with a low wrist shot that beat Emery on the short side.
The Senators dominated play for most of the final 10 minutes of the period, finally tying the score as Neil redirected a one-timer from point-blank range that trickled past Giguere.
Ducks forward Travis Moen, the Game 1 hero, narrowly missed giving Anaheim a 2-1 lead early in the second, ringing one off the left post with Emery prone and out of position.
Notes: The Senators hadn't played at home since losing 3-2 to the Buffalo Sabres in Game 4 of the Eastern Conference final on May 16. ... Former NHL great Brett Hull appeared on Coach's Corner during the first intermission. Hull is now an analyst with NBC.