Motherwell moved a point clear of Celtic at the top of the Scottish Premier League as Hearts' discipline problems continued under Paulo Sergio.
Hearts had Ian Black sent off after 50 minutes after a reckless tackle on Keith Lasley.
And they were made to pay 12 minutes later, when Jamie Murphy rounded goalkeeper Marian Kello to score.
Lasley was also sent off three minutes from time, but Sergio suffered defeat in his first domestic game in charge.
The new manager, who took over from Jim Jefferies last week, was unable to end a run without a league win that has now stretched to 11 games.
For Motherwell, it was a deserved second home win of the season for Stuart McCall's team, although they were given some assistance by a Hearts side who were handed a record £100,000 fine following last season's continued on-field indiscipline.
Michael Higdon had returned from a thigh injury to lead the line for Motherwell, while Steven Saunders was restored to the defence as Robert McHugh and Shaun Hutchinson dropped out.
Sergio, who led Hearts to Europa League victory on Thursday, handed Jamie Hamill his SPL debut following suspension and the wide man replaced the injured Stephen Elliott.
Lasley and Black were both sent off at Fir Park
It was the visitors who were first to threaten when Andrew Driver robbed the careless Saunders and sent in a drive that Motherwell goalkeeper Darren Randolph did well to push behind for a corner.
It was Kello's turn to pull off a good save from Steve Jennings, who had picked up a Chris Humphrey cross at the far side of the box.
In-demand Motherwell striker Murphy squandered the best chance of the first half when he appeared to mis-time his jump and headed Humphrey's cross over the bar from six yards.
Randolph had to rush from his goal to deny Driver after a sliced clearance from Saunders put the home side in trouble.
The Motherwell keeper was forced into another save, this time from Hamill's long-range effort that threatened to sneak in at his left-hand post before the interval.
Hearts were reduced to 10 men when Black, once again showing a short fuse that has hampered his career, went through midfield rival Lasley.
Instead of shutting up shop, Sergio brought on former Motherwell striker John Sutton in place of winger Driver.
However, it was the home side who began to take control and Murphy and Stevie Hammell both squandered chances before the breakthrough finally came.
Eggert Jonsson's poor positioning played Motherwell onside as Nicky Law picked out Murphy and the Scotland Under-21 forward supplied the cool finish.
Tom Hateley sent a dangerous ball flashing across the face of the Hearts goal and Kello turned a Murphy header round the post as Motherwell came close to extending the lead.
Lasley was shown a second yellow card for a late, tired challenge on Arvydas Novikovas, but Well safely negotiated the closing minutes.
Free kick awarded for an unfair challenge on Daniel Grainger by Stewart Carswell. Daniel Grainger has an effort direct from the free kick, Steven Saunders gets a block in.
Free kick awarded for a foul by Eggert Jonsson on Tom Hateley. Free kick taken by Tom Hateley.
Indirect free kick taken by Darren Randolph.
Substitution Jamie Murphy leaves the field to be replaced by Stewart Carswell.
Arvydas Novikovas is ruled offside.
Strike on goal comes in from Rudi Skacel from the free kick.
Dismissal Keith Lasley dismissed for second bookable offence.
Keith Lasley challenges Arvydas Novikovas unfairly and gives away a free kick.
Corner taken by Daniel Grainger, clearance made by Stephen Craigan.
Substitution Arvydas Novikovas comes on in place of Jamie Hamill.
Strike on goal comes in from Stevie Hammell from the free kick, Daniel Grainger gets a block in.
Booking Jamie Hamill is shown a yellow card.
Unfair challenge on Chris Humphrey by Jamie Hamill results in a free kick.
Corner taken by Daniel Grainger from the right by-line, Stephen Craigan manages to make a clearance.
Substitution Rudi Skacel joins the action as a substitute, replacing David Templeton.
Ryan Stevenson takes a shot. Clearance made by Jamie Hamill.
Outswinging corner taken by Tom Hateley, Steven Saunders takes a shot. Comfortable save by Marian Kello.
Jamie Murphy takes a shot. Marian Kello makes a save. Tom Hateley takes a inswinging corner from the left by-line to the near post, clearance made by Adrian Mrowiec.
Shot by Tom Hateley. Ryan Stevenson gets a block in. Inswinging corner taken from the left by-line by Tom Hateley, Marian Kello makes a save.
The assistant referee signals for offside against Keith Lasley. Marian Kello takes the indirect free kick.
Tom Hateley gives away a free kick for an unfair challenge on David Templeton. Free kick taken by Jamie Hamill.
Foul by Jamie Hamill on Nicky Law, free kick awarded. Free kick taken by Darren Randolph.
Foul by Jamie Murphy on Adrian Mrowiec, free kick awarded. Daniel Grainger crosses the ball from the free kick left-footed from right wing, clearance made by Tom Hateley.
Assist on the goal came from Nicky Law.
59:57 Goal scored
Goal! - Jamie Murphy - Motherwell 1 - 0 Hearts Jamie Murphy finds the net with a goal from inside the penalty box to the bottom right corner of the goal. Motherwell 1-0 Hearts.
Stevie Hammell takes a shot. Blocked by Eggert Jonsson. Outswinging corner taken from the right by-line by Tom Hateley, Stephen Craigan produces a header from inside the area that goes over the bar.
Indirect free kick taken by Marian Kello.
Substitution (Hearts) makes a substitution, with John Sutton coming on for Andrew Driver.
The assistant referee flags for offside against Michael Higdon.
Corner from left by-line taken by Tom Hateley.
Shot by Steve Jennings. Jamie Hamill gets a block in. Corner taken by Tom Hateley from the right by-line, Ryan Stevenson manages to make a clearance.
Handball by Ryan Stevenson. Stephen Craigan takes the direct free kick. The ball is swung over by Nicky Law, Michael Higdon takes a shot. Comfortable save by Marian Kello.
Free kick taken by Stephen Craigan.
Dismissal Ian Black receives a red card for serious foul play.
Keith Lasley fouled by Ian Black, the ref awards a free kick.
Nicky Law fouled by Ian Black, the ref awards a free kick. Stephen Craigan restarts play with the free kick.
Unfair challenge on Chris Humphrey by Daniel Grainger results in a free kick. Stevie Hammell delivers the ball from the free kick left-footed from right wing, clearance made by Adrian Mrowiec.
The offside flag is raised against Jamie Murphy. Indirect free kick taken by Marian Kello.
The second half has started.
45:00 +1:49 Half time
Half Time The match has reached half-time.
Keith Lasley fouled by Ian Black, the ref awards a free kick. Stephen Craigan restarts play with the free kick.
Outswinging corner taken right-footed by Tom Hateley from the right by-line.
Jamie Hamill takes a shot. Save made by Darren Randolph.
Free kick awarded for an unfair challenge on Tom Hateley by Jamie Hamill. Free kick taken by Darren Randolph. The assistant referee signals for offside against Michael Higdon. Marius Zaliukas takes the free kick.
Shot by Andrew Driver. Save made by Darren Randolph.
Unfair challenge on Daniel Grainger by Chris Humphrey results in a free kick. Direct free kick taken by Marian Kello.
Unfair challenge on Ryan McGowan by Jamie Murphy results in a free kick. Jamie Hamill takes the free kick.
Jamie Murphy is ruled offside. Indirect free kick taken by Eggert Jonsson.
Steve Jennings challenges Daniel Grainger unfairly and gives away a free kick. Marius Zaliukas restarts play with the free kick.
Direct free kick taken by Marius Zaliukas.
Booking The referee shows Keith Lasley a yellow card.
Free kick awarded for an unfair challenge on Adrian Mrowiec by Keith Lasley.
A cross is delivered by Chris Humphrey, Jamie Murphy produces a header from inside the area that goes over the bar.
Marius Zaliukas takes a shot from 35 yards and missed to the right of the goal.
Daniel Grainger takes a inswinging corner from the right by-line to the near post, Tom Hateley makes a clearance.
Corner taken by Daniel Grainger played to the near post, clearance by Steven Saunders.
Stevie Hammell takes the inswinging corner, Marius Zaliukas manages to make a clearance.
Free kick awarded for an unfair challenge on Chris Humphrey by Andrew Driver. Keith Lasley takes the direct free kick.
Shot from long range by Jamie Hamill goes wide of the left-hand post. Free kick awarded for an unfair challenge on Daniel Grainger by Steve Jennings. Eggert Jonsson restarts play with the free kick.
Free kick awarded for an unfair challenge on Ian Black by Keith Lasley. Free kick taken by Daniel Grainger.
Steve Jennings has a drilled shot. Save by Marian Kello. Stevie Hammell takes a inswinging corner from the right by-line to the near post, clearance by Daniel Grainger.
Corner taken left-footed by Daniel Grainger from the right by-line, clearance made by Nicky Law. Inswinging corner taken left-footed by Daniel Grainger from the right by-line, Header on goal by Eggert Jonsson from inside the box goes harmlessly over the target.
Keith Lasley concedes a free kick for a foul on Ian Black. Direct free kick taken by Daniel Grainger.
Effort from the edge of the area by Nicky Law goes wide of the right-hand post.
Andrew Driver takes the chance to get an effort at goal. Save by Darren Randolph. Corner taken by Daniel Grainger played to the near post, Tom Hateley manages to make a clearance.
Foul by Michael Higdon on Daniel Grainger, free kick awarded. Free kick taken by Marius Zaliukas.
Stevie Hammell takes the inswinging corner, Daniel Grainger manages to make a clearance.
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