Tamika Catchings added 13 points, seven rebounds and a season-high six steals for the Fever (20-9), who have won eight of nine. The Fever are 10-2 since the Olympic break and remain in contention for the top seed in the Eastern Conference playoffs.
Svetlana Abrosimova had 11 points and eight rebounds for the Storm (13-16).
Seattle played without its starting backcourt. Point guard Sue Bird, the Storm's leading scorer, rested and Tanisha Wright did not play because of a groin strain. The Fever took advantage, collecting a season-high 17 steals and allowing a season-low point total.
Seattle center Lauren Jackson finished with four points on 2-for-10 shooting and committed seven turnovers.
Indiana shot just 33 percent from the field, but made 10 3-pointers and outscored the Storm 14-4 from the free-throw line.
The Fever have won at least 20 games for the fourth straight year and are within range of their franchise record of 22 wins with five games remaining. Indiana set the record in 2009, the year the team lost to Phoenix in the WNBA Finals.
The Fever held Seattle scoreless for 4:51 while building a 10-0 lead. Indiana led 35-26 at halftime, despite shooting 32 percent from the field. The Fever forced 15 turnovers before the break.
Indiana led by double digits for much of the third quarter. Seattle closed the gap before Douglas hit a 3-pointer to make it 49-37. A 3-pointer by Jeanette Pohlen and a layup by Erin Phillips late in the period expanded the lead to 56-37. Pohlen drained another three with 0.2 seconds remaining to make it 59-37 at the end of the third.