LeBron James, left, had a huge first half for the Cavaliers last night, pouring in 23 points. Defending for the Celtics are Paul Pierce (34) and Kendrick Perkins.

The Providence Journal / Glenn Osmundson

BOSTON — At halftime last night at TD Banknorth Garden, the Boston Celtics were clearly in a heap of trouble.

Facing a must-win in the always-critical Game Five of their playoff series against the Cleveland Cavaliers, the Celtics had somehow awoken the dangerous LeBron James. After four games of shaky jump shooting, the NBA’s leading scorer was at his very best in a half in which he poured home 23 points and the Cavs led by as many as 14 points.

But James’ breakout game ended after 24 minutes. In a second half ruled by stingy defense and a balanced, unselfish scoring attack, the Celtics came from behind and took control of the series again with a 96-89 victory. Boston can close out the Cavs with another win in Game Six tomorrow night back in Ohio.

James was held to 12 second-half points as he missed seven of the 11 shots he attempted. Beside his game-high 35 points, the only other Cavs to score in double figures were Delonte West (21) and Wally Szczerbiak (10).

The Celtics’ best players played big, with Kevin Garnett going off for 26 points and 16 rebounds and Paul Pierce pouring in 29 points. Rajon Rondo’s quickness was a big factor for the second game in a row and he scored 20 points and dished out 13 assists.

The Celtics led, 88-77, with three minutes left but didn’t close the game out strong. The Cavs scored five points in a row to make it 88-82 and Pierce kept the door open with a missed layup. Szczerbiak then had a wide-open look at a 3-pointer but missed. Pierce hit two free throws to make it 91-84 with 1:05 left, but the Cavs didn’t quit.

This time James drove hard past Garnett and was fouled. He made one of two free throws but Rondo turned the ball over and West swooped in and was fouled. He hit two freebies to make it 91-87 with 45 seconds left. Boston chose to run the shot clock down and was left with a Garnett fallaway at the shot clock that missed but Allen tipped the rebound out to Garnett, who passed to Pierce. He was fouled and the captain’s two free throws made it 93-87 with 15 seconds to play.

After two West free throws, Pierce sank two more clutch shots with 11 seconds left. The Cavs’ West couldn’t get the ball inbounds and Pierce made another free throw, scoring the Celtics final eight points from the foul line.

The first half was a scary scoring exhibition in which the ridiculously talented James flashed most of the skills in his expansive repertoire. He scored 11 points in the opening quarter on 5-for-8 shooting that helped the Cavs to an early 18-9 lead. The Celtics made only four of their first 18 shots, with Pierce really struggling and Allen on the bench after two quick fouls.

The Celts recovered a bit down the stretch and trailed, 23-18, after one. James picked up where he left off in the second quarter as he hit two free throws and made a great penetration move for a 27-20 lead. Two free throws by West and a layup by Daniel Gibson after a loose ball scramble pushed the Cavalier lead to 35-22.

Allen came back into the lineup and he helped instantly with a reverse layup and 3-point shot off a nice feed from Sam Cassell. Garnett’s jumper that bounced around the rim three times before dropping ended a 7-0 flurry to slice the lead to 35-29. James then scored on a power drive, hit two free throws and then took the ball from Allen and was fouled driving to the basket. His two free throws and a gorgeous, step-back 21-footer over Pierce for his 23rd first-half point gave Cleveland a 43-29 lead with 3:48 to play.

The Celtics were just 4-for-12 from the floor in that quarter at that point but they closed with a flourish. A 14-3 closing run began with a Garnett jumper and two 3-point shots from an unlikely source, Rondo. Pierce’s 11-footer with 3.9 ticks left sliced the Cavalier lead to 46-43 at the half.

The start of the third quarter was an offensive feast for the Celtics. They quickly wiped out Cleveland’s lead with the help of two Cavs turnovers. Cleveland battled for a bit but the Celtics made nine of their first 11 shots in the llquarter to grab a 62-57 lead.

Garnett scored eight points during the run, three on jump shots. Pierce snapped a 55-55 tie with a 3-pointer and the Celts kept rolling with Garnett sneaking past Ben Wallace for a bucket and Allen draining a jumper for the five-point edge. At that point, James had yet to score in the quarter and attempted only two shots.

The Celts kept rolling and capped a 12-for-16 (75 percent) shooting quarter with two Garnett assists, one to Glen Davis for a layup and another to Piece for a big-time jam. James scored his only field goal of the quarter on a running floater in traffic with 44 ticks left but the Celts ended the quarter up by nine points, 72-63.

They opened the fourth with Davis scoring again in the lane. When Allen found Davis for a third layup two minutes later, the Celts had taken full control, 76-66.

Next Game

Tomorrow

at Cleveland,

8 p.m.

kmcnamar@projo.com