WASHINGTON — Bradley Beal scored 29 points and the Washington Wizards scored 26 unanswered points in the third quarter en route to a 121-102 win over the Boston Celtics on Sunday night in Game 4 of their Eastern Conference semifinal playoff series.

The Wizards evened the best-of-seven series 2-2 after the Celtics won the first two games in Boston. Game 5 is Wednesday night in Boston.

Beal’s backcourt mate, John Wall, had 27 points despite missing his first nine shot attempts, and he added 12 assists. Washington shot 52.4 percent from the field overall.

The Wizards outscored Boston 42-20 in the third with Wall, Beal and Markieff Morris combining for 34 points in the period.

Isaiah Thomas finished with 19 points for the Celtics, but he scored 15 on 5-of-5 shooting from beyond the 3-point arc in the opening 13:05. Terry Rozier had 16 points and Kelly Olynyk added 14 points for the Celtics.

The series shifts to Boston for Game 5 after the latest two contests followed familiar scripts. Washington won a feisty Game 3, 116-89, after taking control with a 22-0 run in the first half.

On Sunday, after the Celtics broke a 48-48 halftime with the first five points of the second half, they went scoreless for a stretch of 6:28 while committing eight turnovers.

In between, the Wizards went up 74-53 on Otto Porter Jr.’s layup with 5:00 remaining. Porter had 18 points.

Morris contributed 16 points and 10 rebounds. His two free throws gave Washington its largest lead at 86-60.

The Wizards outrebounded the Celtics 45-31 and scored 56 points in the paint.

Washington played without reserve forward Kelly Oubre Jr., who was suspended one game for charging and pushing Olynyk in the second quarter of Game 3 following a hard pick set by Olynyk. Eight technical fouls were called in that game along with Oubre’s flagrant-2 foul.

Tensions didn’t run as hot in Game 4, though Thomas was called for a technical in the fourth.

Thomas scored 33 and 53 points respectively in the series’ first two games, but he was held to 13 points on 3-of-8 shooting during Game 3 as Washington turned up the defensive intensity and pressure.

The 5-foot-9 guard started white hot in Game 4 but attempted only one 3-pointer over the final 35 minutes and never got to the free-throw line. He finished 7 of 14 from the field. Thomas also committed six of Boston’s 20 turnovers.

Washington dominated Game 3 win by maintaining its healthy margin established following a 39-17 first quarter. That’s something the Wizards could not accomplish in the opening two games in Boston, both won by the Celtics.

Boston flipped the script Sunday. The Celtics entered the second up 24-20 when Thomas hit back-to-back 3-pointers. The margin reached 12, but Wall roared from there with all 14 of his first-half points coming in the second quarter.

NOTES: Since Dec. 8, the Wizards are 30-5 at home. … Boston alternated its starting lineup for the fourth time this series by reinserting F Amir Johnson. F Gerald Green started Game 1 and 3 with Johnson in that spot for Game 2. Johnson had seven points in 12 minutes. … PG John Wall has finished with at least 20 points and seven assists in all 10 of Washington’s playoff games this season.