Alex de Angelis claimed his first Moto2 victory of 2012 while champion-elect Marc Marquez fell late on and missed out on sealing the title in a crazy, rain-shortened Malaysian Grand Prix.
The Spaniard's exit means the title remains undecided, although with main rival Pol Espargaro finishing down in 11th Marquez remains a heavy favourite.
The downpour that had earlier delayed the start of the race had an even more marked effect once it started. Conditions ran from treacherously wet to dry and then back in little more than 17 laps, with the havoc of the weather reflected in a massively jumbled track order.
Nowhere was that more apparent than in the form of Malaysian wildcard Hafizh Syahrin who, from 27th on the grid, set a string of fastest laps and had soon moved into a shock lead.
He began pulling away too, but a moment at Turn 1 marked the end of his spell at the front, allowing a trio of chasing riders - de Angelis among them - to close.
Syahrin held on to clinch fourth, but was not a feature of the three-way lead battle that raged over the final laps.
De Angelis held the advantage but with three laps of the official distance to run first Gino Rea and then Anthony West moved ahead. The trio had already been swapping places at the front throughout the opening 15 laps.
As conditions steadily worsened however the race was halted, with Forward rider de Angelis earning the victory as the lap was counted back. West claimed second for QMMF, fractions ahead of Gresini's Rea, as both secured their first ever Moto2 podiums.
While the trio duelled, several other riders had trouble simply staying on the circuit.
Marquez was among them, falling while trying to resist Andrea Iannone four laps from what was the eventual finish.
At the time Espargaro was 13th, meaning that even as Marquez despaired by the side of the circuit he was heading for the title.
Espargaro, helped by several other riders exiting, made his way up to 11th by the finish however. The extra points gained keep the title race alive until at least Australia next weekend, although Marquez needs just two more to secure the crown.
Iannone ended the race sixth, behind Julian Simon, but ahead of Mika Kallio, Bradley Smith and Dominique Aegereter.
Esteve Rabat meanwhile claimed 10th ahead of Pons team-mate Espargaro.
Results - 15 laps (red flag): Pos Rider Team/Bike Time/Gap 1. Alex de Angelis Forward FTR 36m57.793s 2. Anthony West QMMF Speed Up + 0.710s 3. Gino Rea Gresini Suter + 1.363s 4. Hafizh Syahrin Petronas FTR + 2.941s 5. Julian Simon Avintia Suter + 7.583s 6. Andrea Iannone Speed Master Speed Up + 10.062s 7. Mika Kallio Marc VDS Kalex + 23.078s 8. Bradley Smith Tech 3 + 26.957s 9. Dominique Aegerter Technomag-CIP Suter + 30.063s 10. Esteve Rabat Pons Kalex + 31.514s 11. Pol Espargaro Pons Kalex + 31.746s 12. Scott Redding Marc VDS Kalex + 37.108s 13. Toni Elias Italtrans Kalex + 38.627s 14. Axel Pons Pons Kalex + 39.095s 15. Ricard Cardus Arguinano AJR + 40.686s 16. Yuki Takahashi Forward FTR + 40.757s 17. Tomoyoshi Koyama Technomag-CIP Suter + 41.859s 18. Marcel Schrotter SAG Bimota + 46.760s 19. Jesko Raffin Switzerland Kalex + 1m10.712s 20. Elena Rosell QMMF Speed Up + 1m17.807s 21. Marco Colandrea SAG FTR + 1m19.320s 22. Ratthapark Wilairot Gresini Suter + 1m27.281s 23. Simone Corsi Ioda FTR + 1m41.865s Retirements: Thomas Luthi Paddock Suter 14 laps Mike di Meglio Kiefer Kalex 14 laps Marc Marquez Monlau Suter 12 laps Nicolas Terol Aspar Suter 12 laps Jordi Torres Aspar Suter 12 laps Eric Granado JIR Motobi 6 laps Takaaki Nakagami Italtrans Kalex 2 laps Johann Zarco JIR Motobi 0 laps Xavier Simeon Tech 3 0 laps Alessandro Andreozzi Speed Master Speed Up DSQ