Top two Celtic and Aberdeen are in action on Sunday, but Inverness, who are seven points off top spot and four behind the latter team, stumbled as the form book was torn up at Fir Park.
Louis Laing capped a fine team move in the 48th minute to give Motherwell hope of ending an eight-game winless run.
Inverness were unwilling to give up their 10-match unbeaten streak in 2015 without a fight and Edward Ofere headed home Graeme Shinnie's measured cross with 14 minutes to play.
But substitute Lionel Ainsworth fired an 84th-minute winner before a second yellow card for Simon Ramsden left the hosts to close out victory with 10 men.
Motherwell remain at the foot of the table, level on points with fellow strugglers and Saturday victors Ross County and St Mirren.
Jamie Reckord converted Michael Gardyne's pass as County's resurgence continued with a third straight win - 1-0 over Dundee.
St Mirren recorded a maiden home triumph of the campaign by the same margin thanks to Steven Thompson's 63rd-minute strike, which prolonged Hamilton Academical's recent slump.
Partick Thistle secured a first Premiership win in seven attempts thanks to Stephen O'Donnell and a Jaroslaw Fojut own-goal before half time at fourth-placed Dundee United.
Elsewhere, St Johnstone and Kilmarnock shared a goalless draw.
