An injury-time penalty from Paul Hartley rescued a point for Hearts at Fir Park.
Brian McLean scored his first goal for Motherwell after 40 minutes, when he drilled the ball home from four yards after a well-worked free-kick.
Hearts dominated possession but failed to find their usual cutting edge, before McLean's foul on Andy Webster threw them a lifeline.
The Edinburgh side move a point behind leaders Celtic at the top of the SPL.
Hearts were boosted by the return of striker Roman Bednar, who took his place in Graham Rix's squad for the first time since injuring his knee.
However, teenage striker Calum Elliot started in a lone attacking role for the Gorgie side as they opted for a 4-5-1 formation.
It was an unchanged Motherwell side who threatened first with veteran striker Jim Hamilton testing Craig Gordon with a 30-yarder after five minutes which the Hearts man saved comfortably.
In the 25th minute, Scott McDonald's shot from 14 yards was parried by Gordon to Shaun Fagan but the Scotland keeper recovered to push the midfielder's close-range drive over the bar.
The home side broke the deadlock five minutes before the interval, following a clumsy foul by Andy Webster on Hamilton 25 yards from goal.
Kerr played the ball wide right to the unmarked Hamilton and, when his low cross was returned, defender Brian McLean slotted home his first goal since arriving on loan from Rangers.
Hearts looked more threatening after the restart but now they had to find a way past a resolute defence determined to hang on to their lead.
There was a moment of controversy when Rudi Skacel was booked for diving in the Motherwell penalty area following what looked like a robust tackle by Foran.
The incident served to increase the tempo of the game but still the Gorgie side's determination to rely on the high ball was being all too easily nullified by the solid home defence.
Motherwell, dropping deeper and deeper, were relying on the break now with McDonald the outlet.
The Tynecastle side were dominating possession against the increasingly ragged home side but still a lack of composure and guile characterised their play.
In the 70th minute, there was a moment of panic in the home defence when they conspired to leave Skacel free at the back post to take a Simmons cross.
But Well defender Stephen Craigan quickly recovered to block the Czech player's drive from 14 yards.
There was great drama in the final minute when the visitors eventually grabbed the equaliser.
McLean turned sinner when he brought down Webster in the Motherwell penalty area and Paul Hartley slammed home the spot-kick to the relief of the travelling support.
Motherwell: Graeme Smith, Corrigan, Craigan, McLean, Paul Quinn, Kerr, Fagan, McCormack (Kinniburgh 90), Foran (Fitzpatrick 80), Hamilton, Scott McDonald (Clarkson 72). Subs Not Used: Meldrum, McBride, Coakley, Darren Lee Smith.
Booked: Corrigan, Hamilton, McLean, McCormack.
Goals: McLean 40.
Hearts: Gordon, Neilson, Pressley, Webster, Fyssas, Brellier (Simmons 45), Hartley, Skacel, McAllister, Elliot (Cesnauskis 80), Mikoliunas (Bednar 61). Subs Not Used: MacDonald, MacFarlane, Tall, Wallace.
Booked: Elliot, Skacel, Neilson, Hartley.
Goals: Hartley 90 pen.
Ref: I Brines