Craig Brewster returned to haunt his old club as Dunfermline put sorry Dundee United to the sword at East End Park.
The veteran marksman took his goal tally to 10 this season with a double as the Pars cemented their third place in the table just behind the Old Firm.
Scott Walker and Barry Nicholson also struck for the home side while United could only reply through Jim McIntyre.
With Motherwell hitting Hearts for six, the gap at the foot of the table is now only two points leaving United to face a crucial festive programme if they are to pull away from the relegation zone.
The home side started brightly and were ahead after only four minutes.
Some crafty midfield interchanges let Nicholson in on the right for a perfect cross.
Veteran striker Brewster got there ahead of the United defence to slide the ball into the back of the net from 12 yards out.
In the 33rd minute, the visitors enjoyed their best move of the half with Jim Hamilton being denied a goal by a full-length save from Derek Stillie in the Fifers' goal.
However, they were to regret that miss, with Jimmy Calderwood's side grabbing a second and a third before the half time whistle.
Referee Kevin Toner judged that Mark Wilson felled Walker in the area in the 36th minute.
Brewster stepped up and rifled his second of the evening past Paul Gallacher.
Five minutes later, Walker made it three when he rose unmarked at the back post to head a Sean Kilgannon free-kick into the net.
The disgruntled travelling support from the City of Discovery vented their feelings at half-time - booing their team off the field.
But the home fans were celebrating again in the 55th minute when a Nicholson shot from the edge of the area deflected off the hapless Wilson and spun past Gallacher for the fourth goal.
United did manage a consolation strike in the 61st minute when the impressive McIntyre hammered a Steven Thompson pass into the top of the net from six yards.
But, for everyone in Tangerine, it was a miserable evening in Fife which leaves them back in the relegation dogfight.
Teams
Dunfermline Stillie, Skerla, Walker, Scott Wilson, Bullen,
Nicholson, Scott Thomson, Dair (Dempsey 82),
Kilgannon (McGroarty 82), Crawford, Brewster,
Dempsey (Hampshire 87).
Subs Not Used: Ruitenbeek, McGarty.
Goals: Brewster 4, 38 pen, Walker 41, Nicholson 55.
Dundee Utd Gallacher, Wilson, Lauchlan (Duff 58), McCraken,
Paterson, Lilley (Carson 59), Easton, Miller, McIntyre,
Hamilton (Smart 63), Thompson.
Subs Not Used: Combe, Cummings.
Booked: Miller.
Goals: McIntyre 61.
Att: 4,342
Ref: K Toner (Scotland).