Unlike the first four games, in which the Blue Devils (8-1) established an early lead, Williamsport jumped out to an 8-3 edge in the final game behind a pair of Hailee Growden aces and three Jessica Ellis service points.
"I told the (assistant) coach, 'We can't spot them five or six points,'" said Wildcats coach Emily Crabtree. "'We have to jump on them early.'"
But Kortney Eshleman provided a spark for Greencastle with four service points and a kill to tie the score at 8-8. The Blue Devils later erased a 13-10 deficit before successive kills by Cayla Broadwater and Brittany Horn iced it for the Wildcats.
Christine Barnes' 11 straight service points (including four aces) - aided by four Growden kills - broke open the first game, while numerous Greencastle errors and Horn's net play sparked the Game 2 win.
Three straight kills from Rochelle Christman to open the third game provided the impetus for the Blue Devils, while early Williamsport mistakes in Game 4 and a sparkling Greencastle passing game set up the deciding Game 5.
"We've been struggling to play as a team this year," said Crabtree, "and in Games 1 and 2, we got it. We were playing well. Then in Games 3 and 4, we lost that."
Christman paced the Blue Devils with six kills and five blocks, and Amanda Ritchey finished with 16 assists.
Horn led Williamsport with 10 kills. Growden added seven kills, 14 digs and six aces, while Barnes added 34 assists.