Top-of-the-table Northamptonshire appeared on course for a fifth win of the season after taking complete control of their LV= County Championship Division Two clash with Leicestershire at Grace Road.
Leicestershire were battling on 47 for two, still needing another 371 runs to avoid the follow on, when rain brought a premature end to the second day.
Northants added another 247 runs to their overnight 320 for four before declaring on 567 for seven in mid-afternoon.
Kyle Coetzer made a career best 219; Andrew Hall hit his third century of the season and James Middlebrook hammered a quickfire 84. The declaration left Leicestershire with 10 overs to face before tea and they made the worst possible start.
Niall O'Brien gloved behind off a lifting delivery from David Willey without scoring and Lee Daggett took a stinging return catch to dismiss Greg Smith for nine.
Those dismissals reduced the hosts to 19 for two but Ned Eckersley and Joe Burns stayed together until the tea interval, with 19 and 15 to their respective names when the rain swept in to prevent any further play.
An unsettled weather forecast for the next two days could represent Leicestershire's best hope of avoiding defeat after Northants ruthlessly stamped their mark on the game.
Coetzer began the day on 150, but Hall was the aggressor in the opening overs, scoring 35 runs off 32 balls to reach his century from 144 deliveries.
Hall struck 16 fours in compiling a superb knock that ended shortly afterwards on 103 when he drove a catch to cover off Nathan Buck, ending a fifth-wicket stand of 175 in 46 overs.
There was still no respite for Leicestershire with Middlebrook sharing a partnership of 100 alongside Coetzer. The only disappointment for Northants was that they missed out on maximum batting points by just five runs.
Coetzer continued to pile on the misery for the home side, reaching the first double-ton of his career off 371 balls with a six and 36 other boundaries. When he was finally out for 219, caught behind edging a wide delivery from Alex Wyatt, he had batted for just shy of eight-and-a-half hours.
Middlebrook looked set to become the third centurion of the innings until he skied a catch off Rob Taylor. The fall of his wicket brought the declaration, leaving Steven Crook unbeaten with a rapid 47.
Wyatt was the most successful Leicestershire bowler taking 3-107 in 33 overs.