England overcame a last-minute wobble to complete a seven-wicket win over India at Eden Gardens and take a 2-1 lead with one Test to play.
Ravichandran Ashwin (91no) remained undefeated after his valiant resistance on Saturday, but on the final day it took James Anderson (three for 38) only four balls to see off number 11 Pragyan Ojha as India were bowled out for 247 in their second innings.
England were left needing only 41 for a thoroughly-deserved victory, yet then stumbled to eight for three against the spin of Ashwin and Ojha before they got over the line.
Ian Bell and Nick Compton settled the nerves and the issue, and England can therefore no longer lose this series.
For India, it was a first defeat since the last millennium at this famous venue, and England will become the first tourists since 2004 to win a Test series here if they can at least draw the last match in Nagpur.
After dominating the first three days thanks to captain Alastair Cook's batting and Anderson and Monty Panesar's bowling, they endured a chastening first session on Saturday but then took six wickets for only 36 runs in the afternoon. Only Ashwin delayed them, as 88 runs were added for the last two wickets and prevented England finishing the game inside four days.
The number eight immediately counted two more boundaries on Sunday morning too, a high-class back-foot force past cover and a vicious pull past midwicket off Steven Finn.
But in the second over, Anderson snaked one into left-hander Ojha from round the wicket and - even while he was appealing for caught-behind - belatedly noticed he had in fact dislodged the off-bail to at last end a last-wicket stand of exactly 50.
Ashwin had been denied a second Test century, but got his own back when Cook came down the wicket to him in the first over of England's mini-chase and was stumped for only the second time in his first-class career.
When Jonathan Trott was then lbw pushing forward to Ojha, and Kevin Pietersen edged Ashwin behind in defence for a five-ball duck, the unthinkable seemed briefly and horribly possible. But the previously out-of-form Bell, in particular, had other ideas.