A 21-year-old debutant and a bowler in his second Test have helped India rock Australia's bid to reclaim the Border-Gavaskar trophy in Brisbane, where the hosts grabbed a first-innings lead of just 33 runs.
Josh Hazlewood led the way as Australia reduced India to 6-186 in the post-lunch session on day three of the series-deciding fourth Test.
Australia boasted all the momentum, having removed Cheteshwar Pujara, Ajinkya Rahane and Rishabh Pant, and the security blanket of a second new ball to come in the shadows of tea.
But Washington Sundar and Shardul Thakur shifted momentum in scarcely believable fashion, even by the standards set in a topsy-turvy series level at 1-1 with two days remaining.
India were eventually rolled for 336 after a rollicking 67 from Thakur, whose first-class batting average was 16 from 62 games, and Sundar's composed 62 on debut.
The magnitude of Sundar and Thakur's 123-run stand, kickstarted when the latter got off the mark by hooking Pat Cummins for six, will become clear at the end of the game.
But the duo, with a combined one Test worth of experience before being called up as two of four enforced changes for the series finale, have already inflicted several blows to Australia's morale and key men.
Tim Paine dropped a sharp one-handed chance when Sundar was on 45, and the tourists were 6-272.
Paine also squandered two reviews, the latter being a textbook definition of desperation given the second delivery faced by injured tailender Navdeep Saini went nowhere near his glove or bat, after a week in which his captaincy and conduct was criticised.
Milestone man Nathan Lyon's pursuit of 400 wickets, a story arc throughout the summer and especially leading up to his 100th Test, gathered no momentum on Sunday.
Lyon recorded figures of 1-65 from 28 overs, extending a series in which India have regularly frustrated the offspinner.
Paine's team are locked in a race against the clock in Brisbane, where they must win the final Test to end India's four-year hold of the Border-Gavaskar trophy.
Wet weather, which washed out Saturday's final session and is set to interrupt days four and five, has added another degree of urgency to the scenario.
An unheralded Indian XI, in which Pujara and Rahane are the only members who also took part in the series-opening defeat marred by a record-low total of 36, have refused to buckle despite the absence of captain Virat Kohli and other key personnel.
Hazlewood's haul of 5-57 included the key wickets of Pujara and Pant and if Australia manage to secure a 2-1 series victory they will owe him and Pat Cummins a debt of gratitude.
Cummins made a mess of Thakur's stumps to snap the game-changing partnership.
