Marcus Ericsson won a wild GP2 feature race at Spa-Francorchamps, which was interrupted by a huge crash that befell Nigel Melker and caused a lengthy delay.
Poleman Rio Haryanto (Carlin) made a poor start, while Esteban Gutierrez had a flyer from the second row. But he was shoved onto the grass by Haryanto on the inside on the run to La Source. Haryanto thus led from Lotus duo James Calado and Gutierrez.
Ericsson (iSport) jumped past Gutierrez for third at Les Combes, where Jolyon Palmer went straight on after a three-wide battle with Giedo van der Garde and Davide Valsecchi. The latter clipped Fabio Leimer, who spun and was out on the spot.
Calado lost second with a moment at the chicane, which allowed Ericsson past him, and meant Gutierrez then drew alongside his team-mate around La Source. They raced side-by-side down the hill into a yellow flag zone, for Rodolfo Gonzalez going straight on at Eau Rouge on the opening lap.
Despite Calado waving his hand to warn him, Gutierrez passed him under the yellows.
The race was then interrupted by a huge shunt for Ocean driver Melker, who had a twitch through Eau Rouge, which led to a slide at the top of Raidillion that he was unable to recover before impacting the tyre wall head-on at full pelt. He was conscious, but required hospital treatment and was later airlifted out of the circuit.
Moments before that crash, Ericsson had exited Raidillion with far more speed than Haryanto, and passed him for the lead.
Under the ensuing safety car, Gutierrez let Calado back past him for third, which was effectively two wrongs making a right. The stewards did not think so, and later gave Gutierrez a drive-through penalty.
As the mandatory pitstop window opened, all the frontrunners pitted. Haryanto beat Ericsson out of the pits, only to spin the effective lead away at Les Combes as he warmed his cold tyres. Ericsson was fortunate that team-mate Palmer was able to create a space for him to rejoin, as the rest of the field was still streaming in behind him.
After a red flag while the tyre wall was rebuilt, and a further aborted start due to the medical helicopter that took Melker to hospital being absent, the race restarted under the safety car following a lengthy delay.
The first four cars - van der Garde, Stephane Richelmi, Simon Trummer and Stefano Coletti - had all yet to make their mandatory stops, with fifth-placed Ericsson leading the pitters, ahead of Calado and Valsecchi.
Van der Garde led with ease until he made his pitstop at the end of lap 19, and as the others also pitted soon after, so Ericsson was restored to the top spot, and he cruised to a 11.5-seconds victory.
"It's fantastic, two years since I won at Valencia in 2010, but it makes it even more great," said Ericsson. "My guys did a great job in the pitstop. Hopefully I can win a few more."
Calado got stuck behind the tardy Trummer for five laps, which meant his chances of victory were gone, with Valsecchi boosting his title hopes with third place.
"It was very difficult, and I hope Nigel's OK," said Calado. "It was my first time in the dry around here, and I was struggling."
The results remain provisional, however, as Valsecchi's release from his pitstop, that caused Fabio Onidi to stall his Coloni car to avoid a collision, is to be investigated after the race.
"I didn't have the pace to win, but third was a good result from sixth position on the grid," said Valsecchi.
Josef Kral finished fourth, ahead of van der Garde. Luiz Razia, who started 18th after a disastrous qualifying, recovered to an excellent sixth, only losing fifth to van der Garde at the Bus Stop chicane in the closing stages as the Dutchman was on fresh rear tyres.
That meant the Razia and Valsecchi are now level on points at the head of the championship, and it is over to the stewards to decide whether that remains so.
Julian Leal finished seventh, with Felipe Nasr stealing eighth - and reversed-grid pole - at the exit of the very last corner to bring the curtain down on an at-times crazy race.
Results - 25 laps inc stoppage: Pos Driver Team Time/Gap 1. Marcus Ericsson iSport 1h55m36.519s 2. James Calado Lotus + 11.530s 3. Davide Valsecchi DAMS + 13.604s 4. Josef Král Addax + 15.098s 5. Giedo van der Garde Caterham + 15.482s 6. Luiz Razia Arden + 16.903s 7. Julian Leal Trident + 26.615s 8. Felipe Nasr DAMS + 28.903s 9. Stephane Richelmi Trident + 29.230s 10. Rio Haryanto Carlin + 29.568s 11. Esteban Gutierrez Lotus + 31.182s 12. Max Chilton Carlin + 32.160s 13. Daniel de Jong Rapax + 37.340s 14. Nathanael Berthon Racing Engineering + 39.130s 15. Simon Trummer Arden + 49.936s 16. Fabio Onidi Coloni + 54.918s 17. Johnny Cecotto Jr. Addax + 58.788s 18. Ricardo Teixeira Rapax + 1m25.639s 19. Rene Binder Lazarus + 1 lap Retirements: Stefano Coletti Coloni 22 laps Victor Guerin Ocean 21 laps Jolyon Palmer iSport 18 laps Sergio Canamasas Lazarus 11 laps Nigel Melker Ocean 2 laps Fabio Leimer Racing Engineering 0 laps Rodolfo Gonzalez Caterham 0 laps