Cardiff Rugby just came up short in a thrilling Welsh derby in front of a capacity 12,125 crowd at the Arms Park.
They led 12-11 at the interval after two touchdowns from winger Harri Millard who also pulled off a try-saving tackle.
They then fell behind after the break, before setting up a grandstand finish with a penalty try amid a couple of yellow cards for the visitors who had three players sin binned in all.
But Matt Sherratt’s side couldn’t complete the comeback in the closing stages with replacement wing Gabriel Hamer-Webb denied by the narrowest of margins.
So they had to settle for a losing bonus point, as the Scarlets gained revenge for their defeat down in Llanelli a fortnight ago, with prolific scrum-half Gareth Davies claiming two of their three tries.
Tickets had been selling fast for this re-match all week, with just a couple of hundred left on sale at the start of the day.
In the end, the final attendance figure confirmed it was an official sell-out.
That was a big increase on the corresponding fixture last December when a crowd of 8,282 turned out for the visit of the Scarlets.
The bumper attendance followed on from the three successive 12,000 full houses for the home games against Dragons, Harlequins and Connacht in the second half of last season.
Before kick-off, the packed crowd observed a minute’s silence in memory of former Wales coach Kevin Bowring who passed away this week at the age of 70.
With Liam Belcher sidelined by a thumb fracture, Cardiff were captained by centre Ben Thomas, who was to have a fine game, with a new pairing at half-back in Ellis Bevan and Tinus de Beer.
There was also a first competitive start for Irish international prop Ed Byrne who took over at loosehead from the injured Corey Dowachowski, while Efan Daniel started at hooker with both Belcher and Evan Lloyd having picked up injuries against Glasgow last weekend.
When the game got underway, it was the visitors who opened the scoring through the boot of fly-half Ioan Lloyd after their skipper Josh Macleod won a penalty over the ball.
They were then reduced to 14 men when Tongan lock Sam Lousi was yellow carded for dropping onto the lower leg of Daniel, but they still managed to double their lead through Lloyd.
Yet, in the final play before Lousi’s return, Cardiff struck.
From a turnover, Rey Lee Lo set off on a weaving run, with the ball then being moved out to the right where Daniel made good ground.
After a carry from Alun Lawrence, the ball was recycled and that was cue for the start of the Millard show.
Stepping in at first receiver, the left wing sent out an astute pass to put Dan Thomas into a gap.
Flanker Thomas was brought down but offloaded off the deck to Millard who went outside Ioan Nicholas to touch down, with De Beer converting.
Daniel’s part in the try was to be his final involvement as he left the field to be replaced by Daf Hughes.
Once resorted to their full compliment, the Scarlets went back in front when No 9 Davies darted over from close range after Nicholas had surged up to the line.
It looked odds on they were going to extend their lead further when wing Blair Murray escaped down the left and gave an inside pass to No 8 Taine Plumtree who bore down on last line of defence Millard.
But, despite the physical mis-match, Millard succeeded in bringing down the big Wales back row man, with a relieving penalty then resulting.
Another change followed for Cardiff as De Beer limped off to be replaced by Callum Sheedy.
Then, in the final play of the half, prolonged pressure saw the hosts eventually cross the whitewash.
After a series of forward carries, the ball was spun down the line, with Cam Winnett throwing out a long pass, enabling Millard to dive in at the left corner to make it 12-11 at the break.
Soon after the resumption, the lead changed hands once again when Lloyd broke clear in midfield and sent the supporting Davies in for his second.
The Scarlets went further ahead with another converted try on the hour mark as centre Johnny Williams sliced through and went around the last man to touch down under the posts.
But they then had winger Tom Rogers sin binned for a deliberate knock on, with Cardiff immediately capitalising as they earned a penalty try off a lineout maul drive.
That, in turn, saw the Scarlets reduced to 13 men with replacement prop Josh Macleod yellow carded for offending as the maul headed for the whitewash.
With a two player advantage, Cardiff came tantalisingly close to scoring after skipper Ben Thomas broke from his own half, but replacement wing Gabriel Hame-Webb was just forced into touch by a tackle from Blair Murray before getting the ball down in the right corner.
That was as close as the hosts were to get, with the Scarlets holding on for the win.