Kyle Coetzer hit a career-best 217 as Northamptonshire tuned the screw on East Midlands rivals Leicestershire on day two of their Division Two game at Grace Road.
The Scotland international smashed the first double century of his career as the away side progressed from 320-4 to declare on 567-7, with Leicestershire reduced to 47-2 when rain called a premature halt to play at the tea interval.
Coetzer began the day on 150, accompanied by Andrew Hall who was 65 not out at the resumption of play.
Hall was the main aggressor in the opening stages of the day's play, scoring 35 runs off 32 deliveries as he reached his century off 144 balls with 16 boundaries.
But the all-rounder added just three more runs before being caught at cover by Jigar Naik off the bowling of Nathan Buck.
James Middlebrook took up the mantle though and shared in a partnership of 100 with Coetzer, who reached his double hundred off 371 deliveries.
Coetzer was finally caught behind by former Northants wicketkeeper Niall O'Brien after edging a wide delivery from Alex Wyatt, his knock consisting of 36 fours and a six.
Middlebrook appeared on course to become the third centurion of the innings but he skied a catch off Rob Taylor having made 84.
That prompted the declaration to leave Leicestershire with 10 overs to navigate before tea but they were soon in trouble as they slumped to 19-2.
O'Brien fell for a duck after gloving a catch behind to David Murphy after gloving a lifting delivery from David Willey.
Greg Smith then followed him back to the pavilion for nine after falling to a sharp return catch by Lee Daggett off his own bowling.
Ned Eckersely (19no) and Joe Burns (15no) made it through to tea and with it the end of play, with the home side trailing by 520 runs.
Division Two's bottom club will now look to the weather help save them, with showers expected over the next two days.