Former Australia batsman Simon Katich's sensational double-century put Lancashire in control on the third day of their top-of-the-table LV= County Championship Division Two clash with Northamptonshire.
Katich's outstanding 200 off 322 balls included 26 fours and one six as the Red Rose were eventually bowled out for 442, securing a first-innings lead of 132 with David Willey claiming 5-108.
Simon Kerrigan then took three wickets as the hosts closed on 123 for four, still nine runs behind, to set up a fascinating final day at Wantage Road.
Lancashire began the day on 262 for four, 48 runs behind their opponents, with Katich resuming on 114 and Luke Procter 62.
Katich was given a reprieve in the third over of the day when he was dropped by stand-in captain David Sales at second slip off Willey after adding one to his overnight total.
Procter was eventually dismissed for 85, edging Andrew Hall's delivery behind to end a superb fifth-wicket stand of 145.
Willey then struck by trapping Lancashire wicketkeeper Gareth Cross lbw before repeating the trick to Wayne White, who managed just a single. The left-arm seamer knocked over Kyle Hogg's off stump three balls later, meaning Lancashire had lost four wickets for just 17 runs.
However, Katich continued to be the scourge of Northamptonshire by going past 150 off 244 balls in the sixth over after lunch.
His ninth-wicket partnership with captain Glen Chapple set a new record for Lancashire against their opponents, surpassing the 96 made between Ken Grieves and Malcolm Hilton at Northampton in 1955.
Chapple comfortably completed his half-century off 94 deliveries before falling on 57 when he was taken by Hall at slip to give Willey the fifth five-wicket haul of his career and break the stand at 128.
Katich went on to make his fifth double-hundred off 321 balls before smashing the very next ball, bowled by Cameron White, to Muhammad Azhar Ullah at deep midwicket.
Northamptonshire began their second innings after tea and lost Kyle Coetzer in the seventh over when Karl Brown took a superb catch low to his right at third slip off Chapple.
Sales made it to 30 before playing Kerrigan onto his stumps and the same bowler then dismissed Ben Duckett for 24 when his delivery spun into his off stump.
Kerrigan also claimed the wicket of White with five overs left when the Australian chopped on, leaving Northamptonshire in trouble going into day four.