With Celtic having drawn 1-1 against Dundee United at Tannadice in a lunch-time kick-off, the opportunity was there for Rangers to reduce the points deficit in the title race for a third successive week, yet a quite lamentable display by the Ibrox men produced perhaps their worst performance of the season against a team that played with ten men for fully 75 minutes.
Manager Walter Smith fielded an unchanged team from the Aberdeen win two weeks ago against a side that had already defeated Rangers on two occasions this season.
The home side were on the offensive from the opening minutes with Barry Ferguson's stabbed shot from a Dado Prso headflick being turned wide by Caley goalkeeper Michael Fraser in five minutes.
Eight minutes later the game exploded into life when Darren Dods was red-carded for a deliberate body-check on Kris Boyd as the Ranger went through on Ferguson's overhead kick. Referee William Collum had no hesitation in ordering off the defender, and it appeared to be a correct decision.
Just to rub salt into the wound, Charlie Adam opened the scoring from the resultant free-kick from a distance of some 23 yards.
Rangers were now in command - Ian Murray's 25-yard volley following an Alan Hutton cross flashing over in 25 minutes.
There was however a lack of a cutting edge and penetration about the Light Blues' play, and there was almost a sepulchre atmosphere encompassing the near-capacity crowd of 50,278, such was the lack of action surrounding the play.
Boyd was inches wide with a left-foot volley from a Dado Prso headflick in forty minutes, but the half ended without further score.
Boyd again came close three minutes after the restart when he shot into the side-netting from an Ian Murray cross.
Rangers were taking much too long to put this game away - and Boyd once again had a golden opportunity to seal the points on the hour when he was through on a Prso head-flick only to blast the ball straight at Fraser.
Chris Burke replaced Nacho Novo in 67 minutes, but an Inverness side that had scarcely crossed the halfway line were now edging their way back into the game - underlined twelve minutes later when substitute Barry Wilson cut across the eighteen-yard line from a John Rankin pass before firing over.
Boyd yet again was inches away from the killer second when his shot on the turn from a Ferguson pass whistled past an upright in eighty minutes.
Unbelievably however the scores were level sixty seconds later when Craig Dargo turned home Graham Bayne's headflick at the far post with Ian Murray found wanting.
Rangers tried to respond immediately - within four minutes Burke was denied twice, firstly when his mazy run ended with a shot that Fraser held, then, cutting in from the left, his shot was deflected over.
In injury time, Boyd's header from a Burke corner was held by Fraser - and Rangers had thrown away two vital points.
Afterwards a frustrated Walter Smith summarised:
"I was disappointed. We started OK but never imposed ourselves on the game. We never created enough chances in the first-half, but credit to Caley for battling away. Poor defending cost us the goal. The race for second place will go to the wire. We lost the edge to our game we've had recently."
RANGERS McGregor; Hutton, Weir, Papac, Murray; Novo (Burke 67), Ferguson, Hemdani, Adam; Prso (Sebo 81), Boyd
UNUSED SUBS Robinson, Thomson, Ehiogu, McMillan, Shinnie
INVERNESS CALEDONIAN THISTLE Fraser; Tokely, Dods, Munro, Hastings; Hart (Wilson 73), Duncan, Rankin, Paatelainen (McCaffrey 20); Bayne, Dargo (McSwegan 90)
UNUSED SUBS Ridgers, Soane, Sutherland, McAllister
REFEREE William Collum
Attendance 50,278