OKLAHOMA CITY - It wasn't easy and nearly proved too harrowing, not decided until Thunder forward Kevin Durant missed a running jumper with 9.9 seconds to play and his team within two.
Heat forward LeBron James then stepped to the line with 7.1 seconds to play and buried a pair of free throws to close out his 32-point night for a four-point Heat lead.
A game after blowing a 13-point lead in Tuesday's Game 1 105-94 loss, the Heat nearly blew a 17-point first-half lead and an advantage that stood at 15 in the third quarter.
But behind James, this time they held on.
And at this stage, that's all that matters.
The Heat appeared to be set when Durant, the star of Game 1, was called for his fifth foul with 10:31 to play. But he never let up with his offense, draining a 3-pointer and then dunking to draw the Thunder within 82-74 with 8:22 to play.
The Heat then allowed a James Harden basket that drew the Thunder within 82-76.
From there, Heat guard Dwyane Wade and Harden traded baskets, and emerging Heat shooting star Shane Battier and Durant traded 3-pointers, leaving Oklahoma City within 90-86.
A pair of James free throws extended the Heat's lead to 92-86.
But Durant, enduring while saddled with those five fouls, made a free throw to trim the deficit to 92-87.
Wade then scored in the paint for a 94-87 Heat lead, but Thunder guard Russell Westbrook came back with a layup to make it 94-89, with a Westbrook putback basket drawing the Thunder within 94-91 with 1:47 left.
James then stepped up with a deep bank shot for a 96-91 Heat lead.
But back came the Thunder, with as Durant drawing them within 98-96 on a 3-pointer after a Wade turnover.
Following a James miss, the Thunder called time with 12.3 seconds left down two, leading to Durant decisive miss.
As much as anything, the Heat showed that Big Three basketball is back.
With Chris Bosh back in the starting lineup, Wade back in an offensive rhythm and James back to what he has been doing this entire postseason, the Heat survived.
The series next shifts to AmericanAirlines Arena for three Heat home games, starting Sunday at 8 p.m., and continuing next Tuesday and Thursday. With a Game 5 now assured, ticket for that game will go on sale Friday.
The Heat entered aware that only three times has a team overcome an 0-2 deficit in an NBA Finals , something the Heat did on the way to their 2006 championship over the Dallas Mavericks .
Coach Erik Spoelstra didn't want to tempt those odds, so he changed just about everything. Foremost, he returned Bosh to the starting lineup, after Bosh had played the previous four games off the bench following a three-week absence due to a lower-abdominal strain.
Bosh responded with a double-double by the end of the first half, his first in two months, closing with 16 points and 15 rebounds.
Then there was Wade, who was coming off an uneven performance in Game 1. This time he arrived more than three hours before tipoff for extra shooting and responded with a 24-point effort.
That left the Heat enough wiggle room to survive 32 points from Durant, 27 from Westbrook and a 21-point reemergence from Thunder sixth man James Harden, who went from five points in Game 1 to this breakthrough.
If there was any hangover from the Heat's 105-94 Tuesday Game 1 loss, it hardly showed at the outset, as they pushed to a 17-point first-quarter lead, led 27-15 after the first quarter and 55-43 at halftime.
The 43 points were a first-half postseason low for the Thunder. The Heat outscored the Thunder 10-0 on fastbreak points in the first half, the first time in three postseasons they had gone without a first-half fast-break point. There first fastbreak points did not come until 3:53 remained in the third period.
Wade, though, knew more would be needed.
"If we're gonna win," he said during his televised halftime interview, "it's gonna be on the defensive end."
Of course, there also was concern at that stage, considering the Heat blew a 13-point lead in Game 1, with the Thunder seizing control in that second half.
The Heat's 12-point lead at the end of the first was their largest at the close of the opening period in a playoff game in the team's Big Three era.
The Thunder opened 1 of 12 from the field, including an 0-for-5 start from Westbrook, with the only Thunder basket during that run a Durant jumper.
Durant and Westbrook then were forced to the bench with a pair of fouls each in the first quarter. It was the first time this season Durant and Westbrook had two fouls apiece in a first quarter.
But Harden made sure it wasn't going to be easy for the Heat, with 10 points over the final 5:13 of the first quarter and 17 by the intermission, after scoring five in the series opener.
10 points in the opening period tied his career high for an opening period, regular season or playoffs.
This time, James was afforded the luxury of three minutes off the in the first half, with Spoelstra going far deeper into his bench than Game 1, when he essentially played a six-man rotation. This time, Norris Cole and James Jones both entered in the first quarter, each also playing in the second half. Cole was held out of Game 1, with Jones sidelined for the series opener with a migraine.
Spoelstra also shook up the matchups, with James opening defensively against Durant and Shane Batter, who again provided 3-point spark, opening defensively against Thunder center Kendrick Perkins .
When Battier made his third 3-point of the first half it made it 7 of 10 on 3-pointers in the series to that point.
Bosh replaced Udonis Haslem in the starting lineup, giving the Heat their seventh starting lineup of this postseason. The other starters were Battier, James, Wade and Mario Chalmers . It was the first time all season, regular season or playoffs, the Heat had utilized that opening five.