Huddersfield Town supporters wasted no time in serenading the former Addicks forward with a rendition of the 'He's Electric, we signed him from Charlton Athletic' ditty reserved for their top-scorer moments into the game - and he provided the high-energy charge on 25 minutes.
Crossed-wires defending - some would call stupid as Erhun Oztumer, George Lapslie and Deji Oshilaja unwisely attempted to play out from the back on a wind-swept day - saw Grant's eyes light up on 25th minute as he seized on the ineptitude to coolly steer home his 15th goal of the season. It had to be.
And there was gloss at the finish.
Another player who will have contributed significantly should Town retain their cherished Championship status come May in Steve Mounie ensured that Grant had to share the limelight come the final whistle.
With the scoreline still delicately poised with 15 minutes left, Mounie - with quite possibly his first touch - latched onto a fine cross from the impressive Harry Toffolo to double Town's advantage, chesting the ball home from close in to seal a precious victory which turned into an emphatic 4-0 one at the end.
The relief around the John Smith Stadium was palpable with Town helping themselves to a second successive league victory - something they previously did back at the start of November - and provide themselves with a touch of respite at the wrong end of the table in the process.
The party pieces arrived late on when Grant clinically fired home after a lovely flick from replacement Juninho Bacuna - in what proved to be a good day for Town's benchmen.
Bacuna then got in on the scoring act with a blinding stoppage-time strike to help Town record their most emphatic win on the season with a swagger.
Given the status of these sides next to each other in the table, with the pair separated by goal difference only and preoccupied with providing themselves with valuable insurance against the drop, the opener promised to be a big moment and Grant duly obliged - albeit with a fair bit of help from his former cohorts, .
Town failed to hit the heights of their stellar midweek display against Bristol City in the opening half, but it was no 'After the Lord Mayor's Show' either.
The hosts largely showed the conviction and intent and on another day, Grant might have secured rights to the match-day ball by the interval, with Charlton looking vulnerable at the back without the services of Tom Locker and Naby Sarr.
After his opener, Grant was denied by the outside of the post after latching onto the loose ball in a flash after Dillion Phillips saved at the near post after a low shot from Emile Smith Rowe, whose close control and drop of the shoulder to deceive an opponent bore the imprint of class.
Another delectable moment saw Chris Willock and Danny Simpson dovetail well and a cross from the latter was a beauty, but Grant could not direct his header under pressure from Adam Matthews.
Beaten cruelly at Hillsborough in midweek, Charlton were provided with more food for thought at the break and conjured just two half-decent moment in a pretty passive half.
Oztumer's 11th-minute shot after cutting inside was grasped by Jonas Lossl, while the hitherto anonymous Lyle Taylor saw his deflected low shot fly into the side-netting close to the half-time whistle.
Other than that, Huddersfield's defence were not troubled at all.
On the restart, Smith Rowe gave further notice of his excellent technique, with Jason Pearce getting in the way of his well-struck drive which would otherwise have been destined for goal.
Pearce again had to be alert to block a low shot from Trevoh Chalobah, with Town admirably quick to swarm around Charlton when they were in possession in dangerous areas in their own half.
It was a game where the second goal - should it come was likely to be a biggie and fine defending from the alert Toffolo saved the day after good play between Taylor and Matthews.
Play soon swung to the other end, with a piercing mvoe on the break ending with Smith Rowe supplying Willock, whose scuffed low shot was blocked by Phillips.
The Charlton custodian was then called into action to parry a dangerous cross-shot from Toffolo, with home fans howling for a penalty after Fraizer Campbell went down under close attention from Pearce.
Play was opening up with Charlton upping their intensity levels and giving the Town rearguard rather more to think about than earlier.
Smith Rowe then showed delightful close control again before spoiling matters by firing over as the scoreline remains tantalisingly poised going into the final quarter, with Charlton posing more threat on the restart.
That was reinforced when Oshilaja did superbly to get clear down the right, with his pull-back finding Josh Cullen, but fortunately, the ex-Bradford City loanee effort was wild and over the top.
Alex Pritchard then entered the arena to make his comeback after being out since late November as Town sought a relieving second goal.
That duly arrived after Mounie delivered the goods - not for the first time this season - immediately after being thrown into the fray.
Fellow sub Pritchard's flick found the overlapping Toffolo and he crowned an excellent afternoon's work with a fine cross which was steered into the net by the chest of Mounie from close in.
It was the Benin international's eighth goal since December 21. Some going, that.
Grant added the sweetener at the death and this time he did celebrate with more enthusiasm before Bacuna sealed a dream afternoon for the hosts with a stunning fourth.
Huddersfield Town: Lossl; Simpson, Stearman, Schindler, Toffolo; Chalobah, O'Brien; Willock (Bacuna 65), Smith Rowe (Pritchard 70), Grant; Campbell (Mounie 74). Substitutes unused: Coleman, Kachunga, Quaner, Stankovic.
Charlton Athletic: Phillips; Matthews, Pearce, Oshilaja, Doughty; Cullen; Lapslie (Hemed 82), Oztumer (Williams 45), McGeady (Bonne 60); Taylor, Green. Substitutes unused: Amos, Purrington, Smith, Davis.
Referee: G Eltringham (Tyne and Wear).
Attendance: 21,539 (825 Charlton supporters).