Widnes scored two late tries to pull off a comeback victory against last season's Super League Leaders' Shield winners Huddersfield Giants.
After coming from 10-0 down to lead at the break, Widnes did it again from a 20-12 deficit as Joe Mellor and Rhys Hanbury crossed late on.
Hanbury also got the first Widnes try, while Paul Clough scored on his debut and Danny Tickle landed three kicks.
Jermaine McGillvary, Leroy Cudjoe and Eorl Crabtree crossed for the Giants.
Danny Brough kicked two of his three conversion attempts, as well as two second-half penalties when, on top of Crabtree's 50th-minute try, it looked as if he had created a winning platform.
But scrum-half Mellor's converted try 11 minutes from time gave Widnes hope, despite being without skipper Kevin Brown against his old club.
Hanbury scored again four minutes later and, although Tickle missed the kick, the Vikings held on for victory.
The game's opening try came on 10 minutes when Vikings full-back Hanbury spilled a Brough kick allowing McGillvary to pounce for a touchdown.
Another mistake then proved costly when Cudjoe intercepted a Danny Craven pass and sprinted 80 metres for a Brough-converted try under the posts.
It seemed the Giants were in firm control but, having surrendered a 24-6 advantage to be held to a draw by Hull KR last week, Paul Anderson's men switched off again.
Hanbury made amends for his earlier error, side-stepping his way through to score from close range just after the half-hour.
As half-time approached, Widnes then declined a kickable penalty in search of another try and the gamble paid off as Clough, on loan from St Helens, crashed over after Stefan Marsh and Craven had both been stopped just short.
The Giants made a stronger start to the second half with powerful prop Crabtree coming to the fore, winning a penalty and then crashing over from close range to put his side back ahead.
After Brough converted, he then missed a 40-metre penalty, putting that right by landing two more penalties, the first after Willie Isa was placed on report for a high tackle on Kyle Wood.
But Widnes kept pushing and their perseverance paid off when pressure forced a handling error from Chris Bailey, allowing Mellor to nip in under the posts.
The momentum was with them and they remarkably snatched the lead when, after Owens was halted in a three-man tackle in the left corner, the ball came out and Hanbury touched down in the melee.
Widnes coach Denis Betts:
"The confidence they can get from that is immeasurable. It is a fantastic win. A pretty impressive performance against a very good attacking team.
"We were missing some players but we have been working really hard and have just beaten a side that beat us quite convincingly last year. It takes a couple of years to get to this stage.
"One thing we really had to work hard on was our commitment to defence. There are some talented individuals in that team, with a great team spirit, great work ethic and belief."
Huddersfield coach Paul Anderson:
"There is a level of expectation around Huddersfield at the moment which we are failing to live up to. We have got to make sure we respond to that.
"We got outfought. Widnes worked hard and got everything they deserved. Once again we made some things look easy and some things look very hard. Our concentration and attention has to be better. All round we have to improve.
"We probably need to do some practice closing games out. There was a little bit of indiscipline with regard to our systems. We have got to make sure we get a response."
Widnes: Hanbury; Flynn, Dean, Marsh, Owens; Craven, Mellor; Joseph, White, Gerrard, Galea, Tickle, Leuluai.
Replacements: Clough, Johnson, Isa, Lloyd.
Huddersfield: Grix; McGillvary, Cudjoe, Wardle, Murphy; Brough, Robinson; Crabtree, Wood, Kopczak, Ferres, Chan, Lawrence.
Replacements: Bailey, Faiumu, Ta'ai, Kaufusi.
Referee: Robert Hicks (Oldham).