New Zealand will strive to bowl out England tomorrow to advance the match but, at this stage, a result is very much on the cards after the first two tests in the series were drawn.
The match being so finely poised has a lot to do with better bowling from the English this morning.
After beginning the day on 250-1, New Zealand would have resumed with designs on establishing an imposing first innings score before sending in their opponents. But the tourists struck early to dismiss Williamson in the 90s for the first time in his test career.
The 22-year-old, with three test centuries to his name, was caught behind for 91 off the bowling of Jimmy Anderson after showing some atypical indecision to a ball that was seaming away.
His dismissal ended the second-wicket partnership with Fulton at 181 and underlined the fact Ross Taylor has not come to the wicket before the 16th over during this series, another tick in the column of New Zealand batting improvements since South Africa.
When Taylor did come to the crease he was caught and bowled by cheaply Monty Panesar, while Fulton was the last man out before lunch when Matt Prior snaffled a nice catch behind the wicket. Fulton, who eventually fell for 136, will look back on this test fondly after scoring his maiden century, and his wicket left the Black Caps on 312-4 at lunch.
Brendon McCullum and Dean Brownlie began the middle session in fine touch and hit several boundaries to accelerate the scoring rate after a slow morning. But the period on consolidation ended when McCullum gave part-timer Trott just his fourth test wicket from 41 tests, while Brownlie soon cut limply from Jimmy Anderson to pick out Nick Compton at backward point and fall for 36.
That left the bowlers with some work to do at the batting crease, and Tim Southee picked up that responsibility to edge New Zealand over 400. When Southee join BJ Watling some mature batting may have been called for, but that is hardly Southee's style.
He smacked consecutive sixes from the bowling of Stuart Broad and eventually fell for 44 as Steve Finn wrapped up the tail to finish with six wickets.
At that point, day two looked to be a resounding success for England, but Boult snaffled the prized wicket of Cook and, after a review, also sent Trott back to the pavilion.
Compton (12no) and Ian Bell (6no) will resume tomorrow morning.