In a second half highlighted by defense, one offensive play was the difference on the scoreboard.

That’s because the Bengals’ defense made too many big plays to highlight just one.

Mitch Gueller’s 67-yard touchdown catch and a series of key defensive plays down the stretch lifted Idaho State to a 25-21 upset win Saturday at No. 22 North Dakota in the Alerus Center. It is ISU’s first road win in Big Sky Conference play and first victory over a ranked opponent since Oct. 10, 2015, when ISU beat the same school in the same building.

Bengals safety Christian McFarland intercepted UND quarterback Nate Ketteringham on 4th and 11, with the Fighting Hawks 15 yards away from ISU’s end zone and 1 minute, 6 seconds left in the fourth quarter. Running back James Madison picked up the win-clinching first down on ISU’s ensuing possession.

The turnover was Ketteringham’s second of the day and only his second of the season. ISU linebacker Kody Graves picked off UND’s signal-caller early in the third quarter, springboarding ISU’s defensive turnaround.

After the Fighting Hawks rolled up 21 points, 13 first downs and 319 yards in the first half to build a 21-19 lead at the break, ISU’s defense stiffened and held North Dakota to no points, 10 first downs and 150 yards in the second half.

ISU also forced two second-half turnovers, and UND went 1 for 8 on third down after going 5 for 7 in the opening half.

Bengals head coach Rob Phenicie credited the improvements to defensive coordinator Roger Cooper.

“Coop’s adjustments were sound and were the right thing, and it worked,” Phenicie said in a postgame radio interview. “If you shut out a team like North Dakota in the second half, that says something. If you hold a team like North Dakota to (150) yards in the second half, that says something. Our defense stepped up and got after it today. We gave Coop the game ball.”

The teams combined to pile up 669 yards of offense before halftime, including 228 by Idaho State’s ground attack. ISU averaged just under 9 yards per play and never had a scoring drive that lasted longer than 2:40.

But that changed in the second half, when neither team scored until Gueller’s 67-yard catch and run that gave ISU the lead for good with 7:42 to play. ISU and UND combined to gain 103 yards in the third quarter, when neither team converted a third down.

ISU’s rushing attack that gashed North Dakota’s offense early was held to 45 yards after halftime.

“North Dakota came out and really loaded up the box on the run. They were going to force us to throw, and so that’s what we were adjusting to,” Phenicie said. “They were bringing a lot of pressure, and we had to max protect.”

Gueller’s fourth-quarter score was the longest play of the game. It erased numerous missed opportunities, like third-down penalties in UND territory, offensive stalls that turned would-be ISU touchdowns into field goals and a risky 4th-and-1 play that was stuffed by UND in field-goal range.

Gueller’s go-ahead grab was his third and last of the day. He was shadowed by All-American cornerback Deion Harris, who limited ISU’s first-team all-Big Sky wideout to 41 yards receiving before the long touchdown.

“They gave us some man-to-man matchups. That’s what happened on the big touchdown by Mitch,” Phenicie said. “He was manned up by arguably one of the best cornerbacks in the conference. That guy’s awesome. Mitch separated and got the ball and took off.”

But North Dakota (2-2) still had chances to win. The Fighting Hawks blocked Campbell Sheidow’s 48-yard field goal with 3:38 to play, keeping the margin 25-21. UND then drove to ISU’s 15, where a near-touchdown pass from Ketteringham to Brady Oliveira was nixed by the out-of-bounds line and a TD pass breakup by ISU’s Adkin Aguirre and Anthony Ricks preceded McFarland’s fourth-down interception.

ISU had not held a conference opponent to 21 points on the road since a 31-13 win at Portland State in 2014.

“We came together a little bit as a team today,” Phenicie said. “That’s what I saw out of this bunch.”

"Our message at halftime was that we played a bad first half on defense, and we were only down two," Graves said in a postgame press conference. "So if we came out there and played our game, which we did, this would be a half that could change our season ... and not just this season, but a program definer moving forward."

Madison rushed for 106 yards and a first-half touchdown on 25 carries, and backfield mate Ty Flanagan ran for 130 yards on nine carries, including a career-long 55-yarder. Quarterback Tanner Gueller completed 16 of 31 passes for 283 yards, one TD and one interception and was valuable with his legs, adding 70 yards on 10 attempts. ISU finished with 273 yards rushing.

Michael Dean led ISU pass-catchers with 130 yards on nine receptions. Mitch Gueller added 108 yards on three catches.

Sheidow made four first-half field goals, tying for second-most in ISU single-game history. The freshman connected from 44, 38, 22 and 22 yards to account for 12 of ISU’s 19 points in the first half.

“That kept us in the game,” Phenicie said. “You drive down and you dry up in the scoring zone, but you come away with points. That’s all that matters. As long as you do that, you’ll have a chance, and that’s what Campbell did.”

Graves led the defense with 14 tackles, while Caleb Brown and TJ Togiai each had a sack. Togiai’s came on UND’s final offensive series, seven plays before McFarland’s interception.

ISU outgained UND 566-469 and overcame a 3-for-14 effort on third down.

Ketteringham completed 19 of 38 passes for 224 yards two TDs and two interceptions. All-American running back John Santiago gained 114 yards rushing on 13 carries, and Noah Wanzek hauled in five catches for 109 yards and one score.

Idaho State (2-1, 1-0 Big Sky) put a damper on North Dakota’s homecoming Saturday, just in time for a long-awaited homecoming in Pocatello. The Bengals host Northern Arizona next Saturday for their first game in Holt Arena since Aug. 31.

“It’s going to be a battle,” Phenicie said. “We want everybody. Let’s fill that place up.”

NOTES: Idaho State’s inactives Saturday included offensive lineman Garrett Smith, wide receiver Tanner Conner and defensive end Rasheed Williams. Linebacker Paea Moala left the game with an injury after the first play, later returned but was limited and did not record a tackle. The game counts for Idaho State’s conference record, but not for North Dakota’s. The Fighting Hawks are playing an independent schedule this season as they transition to the Missouri Valley Football Conference.