CLEVELAND &

Rising toward the rim, LeBron James cocked his right arm and unleashed four games of frustration on the Boston Celtics.




He's had better dunks. Higher. Harder. Dunks of all shapes and sizes.




None, though, as satisfying.




"There was a lot built up," he said. "That was the play we needed."




James scored 21 points, the final two coming on a devastating slam over Kevin Garnett in the final two minutes, as the Cleveland Cavaliers beat the homesick Celtics 88-77 in Game 4 on Monday night to tie the Eastern Conference semifinal at 2-2.




Back even, and back to Boston &

with authority.




James shook off one of the worst shooting slumps of his life by dominating down the stretch. He finished with 13 assists &

four in the fourth quarter &

and sent the Celtics to their fifth straight road loss in the postseason with a thunderous windmill knockout dunk.




"That," Wally Szczerbiak said, "was phenomenal."




So was the Cavaliers' defense. Cleveland held the Celtics, the NBA's best defensive team, to just 12 points in the final period on 5-of-16 shooting and 39 percent shooting overall.




"We've been able to cover for each other, flying around and contest at the same time," James said. "It's been amazing."




Boston dropped to 0-5 on the road in the postseason, a stunning slip for a team that went 31-10 away from their home floor during the regular season. During a short stay in Ohio, the Celtics lost their momentum in the series but will now head home, where they went 35-6 before the playoffs started.




What's the problem?




"It's hard to say. I have no answer for it," Boston's Ray Allen said.




Game 5 is Wednesday night, and Game 6 will be back in Cleveland on Friday.




James was 7-for-20 from the floor, but he did everything else for the Cavs, who are attempting to overcome an 0-2 deficit for the second time in two years.




In the final 8:45, James had the four assists, dropped a much-needed 3-pointer and delivered the dunk that rocked the rafters in Quicken Loans Arena and became this series' signature moment.




With the Cavs leading 82-75, James drove past Paul Pierce on a screen near the foul line, head faked past James Posey and then posterized Garnett, the league's defensive player of the year. As Cavaliers fans erupted, a scowling James stormed back on defense.




"I just wanted to be aggressive," James said. "I hadn't had a play like that all series. I just turned the corner and saw Posey. I gave him the in-and-out. He went for the fake. Once I turn the corner and get my one-two down, there's not too many guys that can get up and jump with me."




After a timeout, the dunk was shown on the videoboard at least six times, giving Cleveland fans more chances to ooh and ahh at a play they won't soon forget. The Celtics may have a tough time erasing it from their minds.




"He can dunk," Celtics coach Doc Rivers said. "Especially if you give him a running start at the basket. It's probably going to be a pretty good dunk and he's so darn powerful that once he gets up there, there's not a lot you can do.




"I hate the fact that he got to the basket."




The Cavaliers were awed by James' stuff.




"That was incredible," Joe Smith said. "I've seen him do some crazy things since I've been here."




Although their star is shooting only 20-of-78 (26 percent) from the floor, the only numbers the Cavs care about are the pair of 2s that show this series is as tight as possible.




Rivers, too, disagreed with the notion that James is not having a good series.




"You think LeBron is struggling?" he said. "He had 21 points, 13 assists and 6 rebounds. He probably forced 15 fouls. He's making plays."




Garnett scored 15 points, but only two in the second half on 1-of-7 shooting as Anderson Varejao harassed Boston's All-Star. Allen had 15 points and Pierce 13, but the Celtics' Big Three were only a combined 16-of-40.




"They are one of the best defensive teams in the league," Pierce said. "They forced you to drive or take tough outside shots and then their big men collapse."




James missed his first six shots in the fourth before draining a — in front of Boston's bench with 3:17 remaining to give the Cavs a 79-73 lead. After the ball swished through the net, James made an it's-about-time shrug.




After a bucket by Pierce, James dished to Daniel Gibson for a backbreaking 3-pointer as the Cavs opened a seven-point lead.




"They shot two big threes that were daggers," Allen said.




Gibson and Szczerbiak added 14 points apiece, Varejao had 12 and made two awkward jumpers in the final 1:10 to put the Celtics away.




Rivers has been warning his players not to get "mesmerized by LeBron, he's good enough." The Celtics made sure James never got too far from their sights, and when the superstar got loose on a fastbreak, Pierce wrapped his arms around him to prevent a possible dunk.




The players' momentum carried them into a crowded front row, where James' mother, Gloria, told Pierce to leave her baby alone.




"I told her to sit down, in some language I shouldn't have used," James said. "Thank God today wasn't Mother's Day. All I could think about is her. ... I know my mother. It's fine, we're good."




Notes: The Cavs didn't have a turnover in the final 17:51. ... USC star O.J. Mayo, alleged to have accepted money from a sports agency, sat courtside. ... James received four votes, including one first-team ballot, for the NBA's all-defensive team. The 23-year-old's defense has improved greatly over the past few seasons under Cavs coach Mike Brown, who thinks James will someday be recognized for his ability to stop others. "He's only going to get better," Brown said. "I do see him on that first team all-defensive team soon, and I expect to see him there for a long time." Asked who defends him best, James mentioned San Antonio's Bruce Bowen and Sacramento's Ron Artest.