One shot from the right point plus two deflections was just enough to beat Tuukka Rask in the fifth-longest Stanley Cup finals game in history.
Shaw skated in front of the goal in the third overtime and redirected Dave Bolland's shot into the net for the winning score in the Chicago Blackhawks' 4-3 victory over the Boston Bruins in a riveting Game 1 on Wednesday night.
Michal Rozsival started the winning sequence with a shot from the right point into traffic. Bolland tipped it before Shaw got it by Rask for his five goal of the playoffs.
And just like that, the longest Stanley Cup finals game in five years was over.
"We knew it wasn't going to be pretty," Shaw said. "It was a great shot, great shift. It was unbelievable. All the guys deserved this. It was a great battle for us."
Milan Lucic had two goals and an assist for the Bruins, who had won five straight and nine of 10. Patrice Bergeron scored a power-play goal and David Krejci finished with two assists.
Rask made an astounding 59 saves in the longest finals game since Pittsburgh beat Detroit 4-3 when Petr Sykora scored at 9:57 of third overtime on June 2, 2008.
The Blackhawks won for the eighth time in nine games and improved to 10-1 at home in the playoffs.
Game 2 is Saturday night at the United Center.
Jaromir Jagr nearly won it for Boston in the closing seconds of the second OT when the puck deflected off him and hit the post, preserving the tie.
The Bruins were on a power play after Chicago got called for too many men on the ice with 52.8 seconds left in the second OT.
Zdeno Chara's shot from the right point hit Jagr in the slot and deflected off the right post, then bounded through the crease in the waning seconds.
With Original Six franchises playing for a championship for the first time in 34 years, the series is off to a rousing start.
The Blackhawks got third-period goals from Dave Bolland and Johnny Oduya to erase a 3-1 deficit. Corey Crawford was simply spectacular in the extra period, and the Blackhawks wound up going to double OT for the second straight game after taking out the Los Angeles Kings in the Western Conference finals.
Crawford made a sprawled-out pad save on Shawn Thornton about four minutes into OT, and he stood his ground in a flurry with just under eight minutes remaining, stopping Rich Peverley and Tyler Seguin on the rebound to draw oohs and ahhs from the crowd.
In the second overtime, Patrick Kane had a chance to win it. But he fired wide left off the end of his blade from the edge of the crease seven minutes into the period.
Chicago's Michael Frolik just missed high and wide with 6:30 remaining, and Shaw's stuff-in attempt with 3:51 left got stuffed by Rask.
The Bruins appeared to be in good shape building a 3-1 lead in regulation, with Milan scoring twice and Bergeron adding a power-play goal just over six minutes into the third. But the Blackhawks came storming back after that.
Shaw picked off a clearing attempt by Torey Krug and fed Bolland on a two-on-one rush to pull Chicago within one with 12 minutes left in regulation. Lucic then got stopped on a two-on-one by Crawford midway through the third, and Oduya tied it for Chicago when his shot from the point deflected off Andrew Ference and bounced past Rask.
Just like that, the Blackhawks were back in it. Crawford fought off a big flurry by Boston in the closing minutes, and the game went to overtime with Chicago outshooting Boston 39-25 after getting off to a slow start.
The Bruins grabbed a 1-0 lead at the 13:11 mark of the opening period after David Krejci knocked Niklas Hjalmarsson off the puck along the boards behind the net. He fed a pass to Nathan Horton, who feathered the puck across to Lucic for an easy wrist shot from the slot in front of Crawford.
Lucic struck again just 51 seconds into the second period with another wrist shot after Hjalmarsson gambled along the boards and fell, allowing Boston to break in.
Chicago started to come on strong after that.
The Blackhawks got on the board just over two minutes later when rookie Brandon Saad scored his first goal of the playoffs. He carried the puck down the ice but was bumped off it in the left corner of the Boston zone. Marian Hossa recovered it and fed Saad in the slot, making it 2-1 and bringing the sellout crowd to their feet.
The Blackhawks' momentum came screeching to a halt on a power play — make that a two-man advantage — midway through the second. A big issue during the regular season, it continues to haunt the Blackhawks in the playoffs.
They came in 7 for 51 on the power play — 12th among the 16 playoff teams — and that number took another hit when they couldn't convert a five-on three advantage, Horton got called for interference at 7:37 and the Bruins were whistled for having too many men on the ice at 8:20, but Chicago came away empty.
Before Saad's tally, Rask had not given up a goal in 149:36 — he gave up only two goals in a four-game sweep of Pittsburgh — and he saved 54 shots through the first two OTs for the Bruins, who are seeking their second title in three years.
From a 24-game points streak to start to capturing the Presidents' Trophy at the end, no team dominated like Chicago during the regular season. In the playoffs, things haven't been as easy. The Blackhawks took out Minnesota in five games, but had to rally to beat Detroit in the Western Conference semifinals.
They won that one in seven games and didn't blink facing arguably the league's hottest goalie in the conference finals. Instead, they took out Jonathan Quick and the Los Angeles Kings, winning Game 5 in overtime on Kane's third goal of the game to get to this point.
The Bruins, meanwhile, nearly got eliminated in the first round but have been on a roll ever since.
It's a big reversal after they blew a 3-1 series lead in Round 1 against Toronto and fell behind by three in the seventh game.
Then they did something no other team had done. They became the first team in league history to take a Game 7 after trailing by three in the third, with Bergeron scoring the tying and winning goals. Since then, they've made it look easier.
They beat the New York Rangers in five games and swept Pittsburgh, never trailing and allowing just two goals in the series while keeping former MVPs Sidney Crosby and Evgeni Malkin without a point.