Nairo Quintana climbed to a solo victory on stage four of the Tour de San Luis in Argentina but missed out on taking the overall race lead by just four seconds.
The 23-year-old Movistar rider attacked twice on the 10.5km climb to the summit finish on Cerro el Amago, first to pull clear of the peloton and then again to distance fellow escapee Sergio Godoy (San Luis Somos Todos).
He crossed the line 4min 15sec ahead of race leader Phillip Gaimon (Garmin-Sharp), which was just short of his 4min 19sec overnight deficit to the American, but nevertheless sees him jump up to second in the general classification.
Godoy hung on to take second place on the day, 50 seconds back, with chase trio Darwin Atapuma (BMC), Enzo Moyano (San Luis Somos Todos) and Lucas Euser (UnitedHealthcare) rounding out the top five.
There was also a superb performance from Britain's Adam Yates (Orica-GreenEdge), who finished tenth, 3min 5sec behind Quintana. The 21-year-old now rises to 12th overall, 3min 37sec adrift of Gaimon.
The 166.3km fourth stage always promised to deliver drama, with a largely flat day ending with back-to-back categorised climbs.
Five men broke away from the peloton early, but their lead was restricted to just under five minutes as the general classification teams ensured no one would be allowed too big a lead heading on to the final climb.
The remnants of the breakaway were duly caught just before the ascent to Cerro el Amago began, and Quintana wasted little time in attacking to form a new escape.
Gaimon hangs on
Only Godoy could follow and the duo quickly opened up a small gap on a group of chasers and a significant lead over the peloton.
But Quintana then kicked again to leave Godoy behind, before continuing on to an impressive victory that proved he has picked up where he left off last year.
Attention then turned to the plight of Gaimon, who took the race lead on stage one and battled valiantly to narrowly cling on to the orange jersey.
Stage five is a mostly flat 19.2km time trial in San Luis.
Stage four result
1 Nairo Quintana (Col) Movistar, 4:15:33
2 Sergio Godoy (Arg) San Luis Todos Somos, +50sec
3 Darwin Atapuma (Col) BMC Racing, +1:32
4 Enzo Moyano (Arg) San Luis Somos Todos, +1:39
5 Lucas Euser (USA) UnitedHealthcare, 1:45
6 Miguel Angel Rubiano (Col) Colombia, +2:09
7 Peter Stetina (USA) BMC Racing, +2:46
8 Julian Arredondo (Col) Trek Factory Racing, same time
9 Gianluca Brambilla (Ita) Omega Pharma - Quick-Step, +3:04
10 Adam Yates (GB) Orica-GreenEdge, +3:05
18 Phillip Gaimon (USA) Garmin-Sharp, +4:15
1 Phillip Gaimon (USA) Garmin-Sharp, 16:54:41
2 Nairo Quintana (Col) Movistar, +4secs
3 Marc De Maar (Ned) UnitedHealthcare, +1:15
4 Darwin Atapuma (Col) BMC Racing, +1:36
5 Sergio Godoy (Arg) San Luis Todos Somos, +1:45
6 Enzo Moyano (Arg) San Luis Somos Todos, +1:51
7 Lucas Euser (USA) UnitedHealthcare, +1:57
8 Miguel Angel Rubiano (Col) Colombia, +2:18
9 Peter Stetina (USA) BMC Racing, +2:32
10 Julian Arredondo (Col) Trek Factory Racing, +2:47
12 Adam Yates (GB) Orica-GreenEdge, +3:37