Derbyshire 34 for 1 trail Northamptonshire 342 (Bavuma 134, Critchley 4-107) by 308 runs
A superb century from Temba Bavuma put Northamptonshire in a strong position on the first day of the match against Derbyshire at Chesterfield.
The South African Test batsman scored 134, his second hundred in consecutive games, as the visitors recovered from 126 for 4 to reach 342.
Matt Critchley took 4 for 107 but Northants scored 189 in 35 overs in the afternoon and then removed Luis Reece as Derbyshire closed on 34 for 1.
It was a day of contrasts with Derbyshire's bowlers turning the screw in the morning before the batsmen dominated between lunch and tea.
A dry looking pitch prompted Adam Rossington to bat first and variable bounce combined with tight lines made it hard going for the visitors who scored only 66 runs in 29 overs in the first session.
Ravi Rampaul found lift to have Rob Newton caught at second slip but after Luke Proctor edged Fynn Hudson-Prentice low to first slip, Ricardo Vasconcelos was undone by a ball from Reece that kept low.
Bavuma and Rob Keogh, who was dropped on 6, scored only four runs in eight overs before the interval but it was a different game after lunch as Northants moved into overdrive. Keogh faced 81 balls for his 28 out of 81 added with Bavuma in 27 overs but the next 76 came from only 12 with Bavuma and Rossington plundering the spinners.
Bavuma was missed at slip off Matt Critchley on 70 but it was a rare false stroke in an impressive display of concentration and sound judgement punctuated with delightful drives that brought him the majority of his 16 fours.
Rossington was less complicated in taking 38 from 34 balls and with Bavuma dispatching two Critchley full tosses over the ropes, the initiative was now with Northants.
Josh Cobb opened his shoulders to take the visitors to a second batting point before he dragged Critchley to long on but Queen's Park had again lived up to its reputation as a ground where the game can quickly race away.
Critchley was driven into the sight-screen at the Lake End but a quicker ball finally beat Bavuma who was lbw pushing forward with his team one short of a third point.
Hamidullah Qadri found prodigious turn to bowl Zaib but Matt Coles had spectators ducking for cover with 26 from nine balls before he reverse-swept Critchley to point.
Reece was bowled by Ben Hutton in the second over of Derbyshire's reply and although Billy Godleman and Wayne Madsen prevented further setbacks, it was very much Northants day.