After a week during which the club was temporarily shut down because of a flu epidemic, McGhee's ailing players admirably dredged up the desired response - despite being reduced to 10 men as early as the seventh minute by a red card which even the Nottingham Forest manager felt was harsh.
But Forest took command with two second-half goals in four minutes as Leicester discovered that no amount of spirit in adversity on a stamina- sapping pitch could prevent their eighth defeat in 14 matches.
There was nothing incorrect about the sending-off under current rules - Neil Lewis, defending at a corner, used his hand to deny Forest a goal. A penalty award would have been fair enough but a red card for such a misdemeanour seems to be rough justice, equating as it does a mere handball with much more dangerous offences.
"I think a penalty is punishment enough for that kind of thing," the manager said. "It is hardly premeditated violence." And this was not McGhee talking, but Frank Clark.
Stuart Pearce, not surprisingly, was able to cast aside such sympathy as he might have been feeling for Leicester, blasting the spot-kick high into the left-hand corner. This should have been the cue for Forest to take control but, in fact, Leicester looked the better side for the best part of the next hour.
Indeed, they gained a well- deserved equaliser within nine minutes of going behind, through David Lowe's crisp header. Lowe, a striker forced into midfield by Leicester's manpower crisis - six players were absent, through illness, injury or suspension - was a tireless worker among several herculean performers, Mark Blake and Mark Draper being two others.
Eventually though, Forest found the space in which to make their advantage tell and at the same time reinforced their chances of winning a Uefa Cup place. Stan Collymore put them in front, timing his run to perfection to meet Ian Woan's cross with a forthright header and he then returned the compliment as he set up Woan to walk around the goalkeeper for the third.
The aftermath of each goal betrayed Forest's own strife, Collymore being left to celebrate on his own. The striker is in the doghouse with both his manager and his team-mates after publicly criticising them last week and suspending contract talks until the end of the season.
Forest now relaxed and allowed Draper to score from 25 yards to set up a potentially dramatic finale, but an injury-time tap-in from substitute Jason Lee sealed the victory.