wru.co.uk and James Mortimer 17.Nov.2012Getty Images
Wales were behind within two minutes, full back Fa'atoina Autagavaia crossing in the corner. Wales recovered and Ashley Beck's interception try plus the boot of Halfpenny gave them a 13-10 half-time lead.
But George Pisi's acrobatic finish, the boot of his brother Tusiata and Leota's late score gave Samoa the win.
With Wales desperate to bounce back from last week's defeat to Argentina, a quick start was essential. But the crowd had barely taken their seats before Samoa were ahead.
No. 8 Taiasina Tuifu'a stole possession and wrong-footed the Welsh defence to break clear. The Newcastle forward lacked the pace to make the line but the ball was recycled and spread right. With a two man overlap, full back Autagavaia was the beneficiary, touching down in the corner to silence the home crowd.
Fly-half Tusiata Pisi added the conversion as the South Sea Islanders made a fast start.
If the early try showed how dangerous the Samoans could be, a huge hit on Welsh hooker Richard Hibbard demonstrated the intensity of the physical battle.
Wales were struggling to grow into the game and Tusiata Pisi had a chance to extend the Samoan lead but saw his long range penalty fall short.
At 7-0 down, Wales needed some inspiration and Mike Phillips, starting in place of Tavis Knoyle provided it. His quick tap penalty saw Wales on the front foot, earning them a kickable penalty. Halfpenny, who has been so prolific with the boot so far this season, made no mistake from the 10 metre line to narrow the Samoan lead to four.
Samoa's physicality around the ruck was all too evident and Hibbard, perhaps feeling the effects of his earlier knock, was forced off and replaced at hooker by Ken Owens.
Despite some stray passes, Bradley Davies guilty on one occasion, Wales were stringing together a number of phases, something they struggled with last week.
And Halfpenny, who looked Wales' most dangerous attacking threat, soon narrowed the gap with a second penalty.
Following a poor Welsh start, the game was fairly even though both sides failed to create any further clear attacking chances. Leading by a single point, Samoa were looking solid defensively. But just after the half hour, they gifted Wales a way back into the game.
Fly-half Tusiata Pisi was the culprit. With options to his right inside the Wales half, he flung out a hopeful pass. Beck, making his international debut at the Millennium Stadium, intercepted and cantered in for his first Wales try. Halfpenny added the extra two and Wales led for the first time.
Wales and the Ospreys were then dealt a further blow when Dan Biggar was forced off following a tackle from Teofil Paulo at a ruck. The fly-half was replaced by Rhys Priestland but the Scarlet could only watch as Tusiata Pisi added another penalty with the last kick of the half to make it 13-10 at the interval.
With the Welsh injuries stacking up, Ian Evans was replaced by Perpignan man Luke Charteris at the start of the second-half. His first action though was to see Samoa retake the lead. Beck broke down the right wing but saw Samoa captain Lemi turn the ball over. Kahn Fotuali'i emerged with the ball and fed centre George Pisi.
With just inches between him and the touchline, the Northampton Saint showed superb agility to touch down acrobatically in the corner, the score only confirmed after referee Pascal Gauzere had sent the decision to the TMO.
Pisi's brother Tusiata failed to add the conversion but his side clearly took heart from the score.
Halfpenny and Tusiata Pisi then traded further penalties before the Wales man somewhat surprisingly missed a chance to regain the lead on the hour mark.
With Wales trailing 18-16, Halfpenny was soon given a second chance though. From a near identical position to his previous miss, he made no mistake this time round to give his side a one point lead.
With the game on a knife edge, discipline was vital. But from a scrum inside the Wales 22, Gethin Jenkins , who had replaced Paul James, was penalised. Tusiata Pisi kicked the simple penalty to restore his side's lead.
And they made sure of the win when Leota dotted down following Lemi's kick through.