It was the first top-5 matchup in the Pac-12 in 47 years and the last game in the conference’s long and vaunted history.

This first fact is unbelievable. The second fact is unfathomable.

But as No. 3 Washington put the finishing touches on a 34-31 win over No. 5 Oregon in the Pac-12 Championship game at Las Vegas’s Allegiant Stadium — putting themselves in the College Football Playoff as a result — a melancholy set in.

This is all she wrote.

And what a final chapter. Agatha Christie couldn’t haven’t summed it up better.

Drama, intrigue, a massive comeback, a decisive response, jab, duck, hook, duck, repeat. Two Heisman contenders sharing the stage, and not for the last time, in the glitziest city in America. Two coaches in Kalen DeBoer and Dan Lanning who’ve remade their programs in their images in just 2 years. The Huskies, double-digit underdogs, delivering both the first and the final blows, looking tougher and more physical than they had all season. The Ducks, falling behind early but fighting into the final minute.

It was a fitting conclusion to #Pac12AfterDark, one of about 3 things that still make college football fun and pure.

No longer of course. #BigTenAtDusk just doesn’t have the same ring to it.

But what a way to go out.

Speaking of all she wrote, they wrote the book a little early on the Huskies, but Michael Penix Jr. stole the pen.

And he had the last word over Bo Nix.

The game MVP after completing 27-of-39 passes for 319 yards, 1 touchdown and 1 interception, Penix summed up his feelings on the undefeated Huskies coming into the game as 10-point underdogs.

“I gotta say, they tried to write us off,” he told ESPN’s Holly Rowe. “But we ain’t write back. We ain’t write back.”

No, Washington had the first and the last words, with long, drawn-out sentences.

They got on the board first with a 15-play, 54-yard drive that culminated in a Grady Gross 38-yard field goal after chewing up nearly the whole first quarter. Then came an Oregon three-and-out and the Huskies’ first touchdown on a Dillon Johnson 5-yard run (more on him later), and before the Ducks knew it, the Huskies were up 20-3.

Then, after Oregon ran off 21 straight points to claim a 24-20 lead late in the third quarter, Washington went 75 yards and 82 yards in 2 scoring drives that totaled over 10 minutes.

And at the end, with his team clinging to a 34-31 lead with a minute left, it was Johnson who took the ball on third-and-9, let his blockers get into position, then cut back for the decisive 18-yard run and game-sealing first down.

“Overall, it just comes down to execution,” Oregon linebacker Jeffrey Bassa said. “We didn’t execute. We weren’t in the right fits from what it seems like on the field.”

Whether their fits or the fits Johnson gave them, Oregon’s defense looked meeker than it had all year. Johnson — who probably should’ve won game MVP — had 152 yards and 2 touchdowns on 28 carries, constantly gaining yardage despite a long run of just 18 yards.

It was a particular contrast to the Ducks’ usually dominant running game, which was grounded against the far more physical Huskies. That never really happens, someone just owning the line of scrimmage. Yet Bucky Irving had just 20 yards on 9 attempts and Jordan James added 35 yards on 5 carries. Oregon’s best run was Nix’s 44-yard scamper late in the third quarter, but aside from that, the Ducks were largely owned up front.

Nix, meanwhile, struggled with his top target, Troy Franklin, banged up early and for much of the game. Nix had 3 touchdown scores but also an interception and just 239 yards on 21-of-34 passing, by a large margin his lowest completion percentage (61.8%) and lowest passer rating (144.0) of the season.

“The guy threw for three touchdowns,” Lanning said, defending his Heisman contender. “I thought Bo had a great performance. We started off slow early in this game. To have two three-and-outs to start the game off, that put us in a hole. We were playing catch-up a lot of the game. We talked about it at halftime, hey, we’re going to go and score a touchdown here, defense is going to get a stop, we’re going to get an opportunity to pull ahead. We did just that. We weren’t able to maintain that lead.

“Our quarterback gave us a chance tonight.”

But this game wasn’t so much about what Nix or Oregon did or didn’t do but what the Huskies did.

This wasn’t exactly Mike Tyson vs. Buster Douglas, but there was a reason the Huskies were double-digit underdogs against a team they’d already beaten this season.

For much of the year, Oregon has played like Godzilla versus buildings half its size. Is it ruthless to beat teams by 35 on a regular basis? Or is it just routine, when you’ve got the balance on both sides of the ball that the Ducks were blessed with?

And the Huskies were the best darn nerve-wracking team in college football. Has any 13-0 team ever made its fans sweat more?

Washington won its ninth straight game by 10 points or fewer. Six of those games were by a touchdown or less. Four came by a field goal or less, including their last three.

The Heart Attack Huskies, though, always found a way to toughen up when it mattered, and it’s that physical edge that has them headed to the Rose Bowl, where they will likely have that physicality put to the test by No. 2 Michigan.

“I think we always draw on our experiences,” DeBoer said. “There is a deep, deep, deep belief right now in our football team that when the moments get tough, we can really hone in and guys will just do their job. Not get overwhelmed, go execute. I think, again, can you go back to one game and learn from it. You can go back to all of a sudden two or three.

“Everything has happened in a different way. We’ve won it in different ways. Man, we got a brotherhood in that locker room that is super proud, wants to continue to showcase who they are collectively and how hard they play, how much they love each other. It shows. It shows.”

So…that’s it.

The Pac-12 packs up its tent and heads back to San Francisco to prepare to become the Pac-2, hoping to rebuild from the ashes of college football carnage.

It’s fitting that the league had one last late-night soirée, and even more appropriate that it delivered.

Washington heads to the CFP carrying the weight of a dying 98-year-old conference on its able shoulders.

Can it breathe some life into the Conference of Champions for just a little longer? One last gasp?

If anyone can, it’s the Heart Attack Huskies.