Whether or not it is validated by a berth in the World Test Championship final, this was the kind of day that illustrated why New Zealand are in the mix for that spot. There are few days in this format when the axis of a game turns so markedly within the space of a session even while appearing to have occurred by stealth. That Kane Williamson was at the heart of such a silent ambush is of little surprise, but, to borrow a phrase more commonly pressed into service in football, the one-sided scoreline didn't really reflect the ebbs and flows of a delightfully entertaining day's play.

That New Zealand ended the day just 11 shy of Pakistan's 297 having lost just the three wickets is little short of an insult to the first two sessions, a period of cagey, nervous New Zealand batsmanship quite distinct from the breezier approach Pakistan adopted the previous day. After Tom Latham and Tom Blundell were worn down by the nagging consistency of Pakistan's quicks and Ross Taylor's Christchurch blues condemned him to another failure, New Zealand suddenly found themselves receiving a dose of the medicine they had so effectively served Pakistan at Bay Oval.

While Pakistan had flirted with boundaries just after lunch on day one at Hagley Oval, New Zealand were significantly more laboured around the same time on day two, having barely kept their run rate bobbing above two. Pakistan were prowling, and Henry Nicholls, who has enjoyed a very productive summer, looked particularly exposed early on. New Zealand were trailing by over 225 runs, and the usefulness of Pakistan's proactive approach with the bat the previous day became clearer by the over.

As much as the day ended up belonging to the unbeaten 215-run partnership between the irrepressible Williamson and the gritty, if streaky, Nicholls, Pakistan have only themselves to blame for having had to spend the last six hours of the day bowling at the pair they will by now be sick of the sight of. When New Zealand had walked away with what could only be described as a steal of a series win against Pakistan in the UAE two years ago, these were the two men who topped their team's run charts, averaging 77.20 and 57.40 respectively. It was the series that seemingly cemented Nicholls place in a very competitive New Zealand middle order. An assist from the same opposition looks set to help him begin 2021 in the perfect manner.

On a day when deadlock dominated the first half, the vision to seize the moment that broke the game open for his side was just as impressive as anything Williamson would go on to do with the bat

Shaheen Afridi had him nick off in the 33rd over with the score on 74, with Rizwan, as you might expect, completing a superb catch. Nicholls, who had walked off in the previous Test when he wasn't actually out, was about to depart once more when the umpire declared Shaheen had overstepped. Hindsight tends to play tricks with the mind, but Pakistan have bowled 20 no-balls so far this series, and this felt like one that would really make them pay.

Even so, Pakistan's hold on the game hadn't loosened much an hour later. With tea approaching, New Zealand had limped along to 106, and while Williamson and Nicholls were hanging in there, they had combined to score 32 of 111 balls. It was in marked contrast to the positivity Azhar and Rizwan had displayed under pressure in the middle overs, and Pakistan's first-innings total still looked reasonably impregnable.

Rizwan has hardly put a foot wrong either as keeper or batsman for the best part of six months, but four overs before tea today, he would throw the ball to part-timer Shan Masood. It might have been a gamble - Masood once removed Hashim Amla off the final ball of the day in Cape Town - or the seamers may simply have needed a breather. However, Pakistan did have a genuine fifth-bowling option in Zafar Gohar, who hadn't yet sent down a single over.

It was a momentary drop in both intensity and quality, but like a predator having hunkered down awaiting his moment, Williamson sprang to life. Masood to Williamson was a combination that happened for just six deliveries all day, but a man who had inched to 21 off 72, surviving another tough chance in the slips along the way, took 13 runs off them. The 50 partnership was up, and suddenly, as a Haris Sohail over sent the players in to tea, the scoreboard read a more assured 145 for 3.

From thereon, Williamson was a man uninhibited. He would score 91 off the next 103 balls, especially punishing the length deliveries he had spent gently negotiating before tea. Pakistan's drop-off played its part, of course, and in many ways the first phase of Williamson's innings equalled the second in the effectiveness with which it showcased his brilliance. Mohammad Abbas and Faheem Ashraf probed especially thoroughly before tea, but a casual viewer might have missed that for the ease with which Williamson kept them at bay. There were no plays-and-misses, no bats hung out to tempt the outside edge, and little reason for the in-field to become excitable to create a feedback loop of pressure. Those length balls saw the New Zealand captain score just 18 runs in 60 deliveries, with little warning of the incipient danger to Pakistan's chances. After the 46th over, he would score 50 off 51 deliveries in the same area.

Recognising that the pace had begun to drop and the scoreboard pressure that gave Pakistan such a hold over the game no longer existed, he spent the final session either getting in line and pulling the bowlers in front of midwicket, or waiting as late as only Williamson does and easing them behind point. It was classic, typical predictable Williamson, and in that sense there may be nothing remarkable about the innings that brought up his 24th century. But on a day when deadlock dominated the first half, the vision to seize the moment that broke the game open for his side was just as impressive as anything he would go on to do with the bat.

By stumps, New Zealand's scoring rate was 3.36, a shade below Pakistan's 3.55 the previous day, despite having hovered around two for the first 45 overs. The latter parts of the day made the greatest impression on the scorecard, with New Zealand adding 131 in 35 overs as Williamson unfurled his dazzling repertoire of strokes. But on a day that Pakistan arguably controlled for longer, it was the timing of New Zealand's onslaught that sees them take a vice-like grip of this second Test. Pakistan may rue the unforced errors and the occasional tactical misstep, but on a bright sunny day when the slightest let-up would have put Pakistan in control, Williamson's New Zealand ensured they were left out in the cold.

Danyal Rasool is a sub-editor at ESPNcricinfo. @Danny61000