Colombia's Rigoberto Uran produced a sensational individual time trial to win stage 12 of the Giro d'Italia and take the overall race lead.
The Omega Pharma - Quick-Step rider completed the hilly 41.9km course in 57 minutes 34 seconds, 87 seconds quicker than Italy's Diego Ulissi in second.
And Uran's time was 94 seconds better than Cadel Evans, who held a 57-second overall lead going into the stage.
Australian Evans dropped to second, 37 seconds adrift, with nine stages left.
With the riders heading out in reverse order, Uran was the penultimate rider down the start ramp in Barbaresco and, by that time, Ulissi, a winner of two stages on this year's Giro, had set the quickest time of the day.
But Uran was quickest through the first intermediate checkpoint, which came after the opening 12km of predominantly uphill racing, and maintained his momentum through the flatter middle section before extending his lead on the final ascent to the finish.
"I am really surprised," said Uran, who becomes the first Colombian to wear the Giro's pink jersey as race leader. "With it being a time trial, I didn't think I would win it, but it is a superb day."
Evans finished third to keep himself in contention for the overall race victory, while Rafal Majka finished fourth on the stage and is fourth overall, almost two minutes back.
Pre-race favourite Nairo Quintana finished 13th, 2:41 behind compatriot Uran and is now 3:29 adrift in the general classification.
The race features six mountain-top finishes in the remaining nine stages, which should suit Movistar rider Quintana, although whether he can claw back the time he has lost on adept climbers Uran and Evans remains to be seen.
Friday's stage 13 takes the riders 158km from Fossano to Rivarolo Canavese.
Stage 12 result
1. Rigoberto Uran (Col/Omega Pharma - Quick-Step) 57:34"
2. Diego Ulissi (Ita/Lampre) +1'17"
3. Cadel Evans (Aus/BMC Racing) +1'34"
4. Rafal Majka (Pol/Tinkoff - Saxo) +1'39"
5. Gianluca Brambilla (Ita/Omega Pharma - Quick-Step) +1'53"
6. Wout Poels (Ned/Omega Pharma - Quick-Step) +2'00"
7. Wilco Kelderman (Ned/Belkin) +2'03"
8. Thomas De Gendt (Bel/Omega Pharma - Quick-Step) +2'07"
9. Domenico Pozzovivo (Ita/AG2R) +2'09"
10. Patrick Gretsch (Ger/AG2R) +2'12"
1. Rigoberto Uran (Col/Omega Pharma - Quick-Step) 49:37:35"
2. Cadel Evans (Aus/BMC Racing) +37"
3. Rafal Majka (Pol/Tinkoff - Saxo) +1:52"
4. Domenico Pozzovivo (Ita/AG2R) +2:32"
5. Wilco Kelderman (Ned/Belkin) +2:50"
6. Nairo Quintana (Col/Movistar) +3:29"
7. Fabio Aru (Ita/Astana) +3:37"
8. Wout Poels (Ned/Omega Pharma - Quick-Step) +4:06"
9. Steve Morabito (Swi/BMC Racing) +4:20"
10. Robert Kiserlovski (Cro/Trek) +4:41"