England lost the key wicket of Joe Root late on a dramatic first day to leave the fourth Test with India finely balanced at the Kia Oval.
Root was bowled by Umesh Yadav for 21 to leave the hosts 53-3 after they had bowled India out for 191.
Opting to bowl on winning the toss, England exploited the assistance on offer, Chris Woakes taking 4-55 in his first Test in more than a year and Ollie Robinson continuing a super start to his international career with 3-38.
Despite 50 from captain Virat Kohli, India found themselves 127-7, only for Shardul Thakur to crash a 31-ball half-century, the fastest in Test cricket in England.
India lost their last three wickets in four balls, then reduced England to 6-2 - Rory Burns fell for five and Haseeb Hameed nought, both to Jasprit Bumrah.
Root and Dawid Malan looked to have weathered the storm, only for Umesh to trim the bails and send captain Root on his way for 21.
It left nightwatchman Craig Overton to see England to the close alongside Malan, who is unbeaten on 26.
Chaotic day mirrors fluctuating series
This has been a fluctuating series, the nature of which was reflected on a chaotic and, at times, bizarre opening day.
India once again ignored the 413 Test wickets of Ravichandran Ashwin and promoted Ravindra Jadeja to number five in the batting order.
Even though England worked their way through the India batting, they still dropped four catches and were flayed by Thakur.
When Burns played on to his own stumps and Hameed loosely edged a cut in the same over, there was a real danger of India wreaking havoc in the final hour.
As ever, Root was a reassuring presence, and the 46 he added with Malan looked to have England in control.
Umesh, though, hurried a nip-backer between the captain's bat and pad, giving India an opening to exploit on Friday morning.
Woakes' dependable return
Woakes was England's player of the year in 2020, yet went more than 12 months without playing a Test through a combination of injury, being rested and being forced to isolate.
Despite having little match practice, he made a typically seamless return, in place of the omitted Sam Curran. On top of his four wickets he had two catches dropped and an lbw decision against Ajinkya Rahane overturned.
Woakes struck with only his sixth delivery, finding extra bounce to take Rohit Sharma's edge. Jadeja poked to first slip and Rishabh Pant carelessly slapped to mid-off before Woakes ended the Thakur assault by earning an lbw on review.
There were times when England were not at their absolute best - James Anderson started off expensively and Robinson was occasionally down on pace - but they were still good enough to torment the vulnerable India batting.
Only when Thakur got going did England lose control, yet his downfall was the signal for the final three wickets to fall for one run.
After Thakur fell to Woakes, Bumrah was run out without facing by Burns' direct hit after Overton dropped Umesh, well Jonny Bairstow, back behind the stumps, took a fine one-handed catch to hold Mohammed Siraj and give Robinson his third wicket.
Thakur reverses momentum
While the rest of India's top order showed little aptitude for repelling the England attack in helpful conditions, captain Kohli batted with control and class.
Shuffling across his stumps, he played wonderful off-drives, surviving being dropped by first slip Root off Woakes on 22.
Still, when Kohli turned the face of the bat on Robinson to be caught behind, it confirmed that a wait for a Test hundred stretching back to November 2019 will continue, with Ajinkya Rahane and Pant following soon after.
Enter Thakur, who was preferred to Ashwin, to defiantly reverse the momentum with some wild swiping and clean hitting.
Overton was lofted over long-off for six, Woakes suffered the same fate from a hack to cow corner and Robinson was crunched over deep square leg.
Thakur was dropped by Bairstow when he followed a Robinson short ball on 43, going on to complete the second-fastest half-century by an India batsman in Test cricket. His fifty stand with Umesh came up in only 6.4 overs.
Even though Thakur's departure was the beginning of the end of India's innings, they carried the fight into their bowling, claiming the trio of wickets that leave the match in the balance.
'The game's in the balance' - what they said
England all-rounder Chris Woakes on BBC Test Match Special: "I'd have snapped your hands off for 4-55 at the start of the day.
"Fair play to Shardul - he got after us a bit and played some good shots - but to bowl a team out for 190 on day one is a really good effort."
Former England captain Michael Vaughan: "It's been a very good day for bowling, but it's been a poor day for the craftmanship of Test match batting.
"You can't tell me, with the talent in these two sides, that someone shouldn't be getting a big score on that pitch. I'm trying to give them all the excuses in the world, but I can't.
"At tea time, I thought India were completely out of this Test match. Well, they've won that last session with Thakur's innings and those three wickets. The game's in the balance."
