SANTA CLARA, Calif. — It came apart bit by bit for the Detroit Lions, slowly at first and then seemingly all at once.

A risky fourth-down call. A bobbled interception that turned into a big gain. A bungled handoff that led to a fumble. A dropped pass. A wasted opportunity on special teams. And too many missed tackles to count.

The Lions played their best first half of the season in Sunday’s NFC championship game, then crumbled in the second half amid a slew of self-inflicted errors, losing a heartbreaker to the San Francisco 49ers, 34-31, at Levi’s Stadium.

READ MORE: Lions' NFC title game loss to 49ers is franchise's worst meltdown

"That's not like us," a somber Lions coach Dan Campbell said after the game. "That hasn't been on us all year, and it showed up today, at the worst time."

The Lions fell one win short of reaching the Super Bowl for the first time in franchise history, bringing their storybook season to an end at a stadium 37 miles from their last road postseason victory 66 years ago.

The Lions beat the 49ers, 31-27, at old Kezar Stadium on Dec. 22, 1957, to advance to the NFL championship game, where they beat the Cleveland Browns. They haven’t played for a title since, and will have to wait until next fall to try again.

For 30 minutes Sunday, the Lions seemed bound for Super Bowl LVIII in Las Vegas. They moved the ball at will against a 49ers team that finished third in the NFL in scoring defense in the regular season and shut down San Francisco’s high-powered offense.

But the Lions’ Super Bowl dreams disappeared like a mirage in the Las Vegas desert when they gave up 27 straight points in the second half.

Trailing 24-7 at halftime, the 49ers kicked a 43-yard field goal on the opening drive of the third quarter then steamrolled their way to scores on their next four possessions.

The comeback started when the Lions failed to convert a fourth-and-2 from the 49ers’ 28-yard line midway through the third quarter. As has been the case for most of his three seasons as Lions coach, Dan Campbell passed on a 46-yard attempt to try and pick up the first down.

Jared Goff stepped up in the pocket to avoid pressure on the play, and threw a touch wide of Josh Reynolds beyond the sticks, who got two hands the ball but could not secure it.

The 49ers answered with a five-play, 72-yard touchdown drive to cut their deficit to 24-17. Brandon Aiyuk caught a 51-yard heave from Brock Purdy two plays after the failed conversion on an overthrown pass that bounced off Lions cornerback Kindle Vildor’s hand and facemask and gave the 49ers a first-and-goal at the 4.

Jahmyr Gibbs fumbled on the first play of the Lions’ next offensive possession, after a taking a bungled handoff from Goff. And the 49ers tied the game at 24 four plays later on Christian McCaffrey’s 1-yard touchdown run.

The Lions went three-and-out on their next series, after Reynolds dropped a would-be third-and-10 conversion, and the Lions failed to down Jack Fox’s ensuing punt inside the 5-yard line when Chase Lucas ran into the end zone.

Purdy completed 20 of 31 passes for 267 yards with one touchdown and one interception, and scrambled for 52 yards on three carries in the second half.

READ MORE: So. Flipping. Cruel: Lions 34-31 loss to 49ers puts damper on otherwise great year

The 49ers took a 27-24 lead on a 33-yard field goal by Jake Moody with 9:52 to play, and after Campbell passed on a 48-yard field goal attempt on the ensuing possession, only to watch Goff throw a fluttering fourth-and-3 pass that fell short of a completion to Amon-Ra St. Brown, they tacked on another touchdown on a 3-yard run by Elijah Mitchell.

Goff led the Lions on a late touchdown drive, throwing a 3-yard scoring pass to Jameson Williams with 56 seconds to play, but after an illegal touching penalty on the ensuing onside kick, the 49ers ran three plays and took one kneel-down snap after a delay-of-game penalty with 1 second left to run out the clock.

Goff, a Bay Area native who now has lost six straight games to the 49ers team he grew up rooting for, finished 25 of 41 passing for 273 yards and one touchdown, and Gibbs, David Montgomery and Jameson Williams ran for first-half scores for a Lions team that set a franchise record for most wins in a season (14, including the playoffs).

The 49ers tied their own record for biggest comeback in an NFC championship game, and will play Patrick Mahomes and the Kansas City Chiefs in the Super Bowl on Feb. 11.

McCaffrey finished with 20 carries for 90 yards and two touchdowns, and added another 42 yards receiving, and Deebo Samuel had 89 yards on eight catches for the 49ers, who played in the NFC championship game for the fourth time in five years.

Lions fans: Celebrate a renaissance 2023 season with a new book from the Free Press.

Contact Dave Birkett at dbirkett@freepress.com. Follow him @davebirkett.

This article originally appeared on Detroit Free Press: Detroit Lions suffer brutal collapse to 49ers, one win from Super Bowl