When your luck is out, it is really out.
Following the own-goal, penalty and red card of Yeovil the previous weekend, it was a wicked deflection which paved the way for a fifth home defeat of the season.
The Addicks performed admirably but it was a familiar case of failing to carve out enough clear-cut chances to ensure anything from a game in which, for large parts, they were the better side.
But nothing can be taken away from Derby County's professional performance as they took advantage of their hosts' shortcomings in the final third, adding a killer second in the dying embers of the game to extinguish Charlton's hopes of a point.
Chris Powell shook up his starting XI before kick-off, moving to a 4-5-1 formation.
Danny Green was the notable inclusion, making only his second start of the campaign, and first since the Valley defeat to Middlesbrough in August with Johnnie Jackson sitting out the first of his three-game ban.
Bradley Pritchard was thrust back into the side once again after missing out on the previous four games as Simon Church had to settle for a place on the bench.
The first sight of goal came 10 minutes into proceedings. And it came through an unlikely source.
As stand-in skipper Michael Morrison picked up the ball in an advanced position, he was urged to shoot by the Valley faithful.
And shoot he did. His good-looking effort was hit low to Derby stopper Lee Grant's right who got down well to make the block.
It represented a positive start for Powell's men who were knocking passes around neatly in the opening exchanges.
Another half-chance fell to Dale Stephens after 14 minutes.
The troublesome Cameron Stewart found space to send in a left-wing delivery and, with Stephens waiting, he was in the perfect position to send a volley goalwards.
But the midfield maestro should have done better, not least due to his already impressive volley copy book, as he sliced his first-time effort well wide.
Shortly after, Green's deep set-piece delivery nearly caught out Grant, whipping it in from the left as the Rams' custodian scrambled to tip it over from underneath the bar.
The Addicks were enjoying the majority of possession and were looking far more likely without creating that all important clear-cut opportunity.
It very nearly came on 23 minutes when a superb piece of skill from Kermorgant sent in Pritchard who had snuck in behind the Derby defence.
The returning midfielder would have found himself one-on-one but for Richard Keogh's timely interception as the Rams' skipper was just able to hook away.
If you fail to make your mark while on top you are, unfortunately, always susceptible to a set-back.
And Charlton discovered just that to their detriment after 32 minutes when the visitors took the lead, albeit through a huge slice of luck.
When Jamie Ward won a free-kick for his side 25 yards from goal, the attacker stepped up himself.
His effort bounced off the Addick's wall taking the ball out of the reach of Ben Alnwick and putting the Rams 1-0 up.
Charlton did not deserve to be behind but as it was, they would head into the break in preparation for an uphill struggle in the second-half.
Indeed, it could have been worse but for an eye-catching Alnwick save just before half-time.
Craig Bryson hit his shot viscously from just outside the box and it looked to be heading for the top right-hand corner. But the Addicks' goalkeeper flew to his left to tip the ball out for a corner.
The hosts began the second period with a good flowing move down the right-hand side.
With Lawrie Wilson making the overlapping run, he delivered a dangerous cross which fell to Stephens who let it bounce before trickling his half-volley just wide.
There was no doubting the Addicks' ability to create half-chances. But the underlining issue remained that they simply were not creating anything meaningful.
Morrison tried to scramble in an effort with his back to goal on the hour but it was another example of Charlton being the 'nearly men' in front of goal.
And for all the while they were struggling in front of The Covered End, Steve McClaren's side always looked dangerous in front of The Jimmy Seed Stand.
Ward came inches away from doubling up when his shot from just inside the area came crashing back off the bar from Chris Martin's cut-back to prove that Charlton could not rest on the lion's share of their possession.
The Addicks needed a resurgence, and Powell was hoping it would come with a double switch in the 65th minute as both Church and Callum Harriott entered the fray in place of Green and Pritchard.
And the immediate change brought about some positivity in the Addicks, creating their best opportunity up to that point seven minutes later.
Kermorgant delivered a fine cross, wrapping his right food round the ball to deliver it to the back stick. Morrison was on the end of it as he hared towards the far post but his connection took the ball just wide with inches in it.
A series of missed fouls and controversially awarded free-kicks saw Kermorgant end up in referee Andy Davies' book in bizarre circumstances. The Frenchman applauded the man in black after winning his side a free-kick, but with Davies viewing his clap as a form of dissent, he brandished the yellow card somewhat harshly.
It put fire in Charlton's belly and their tails were up.
Church was sent through with 10 minutes remaining but could only hit his first-time effort straight at Grant as the Addicks camped in Derby's half.
But as they huffed and puffed in search of an equaliser, the Rams dealt a killer blow with three minutes remaining.
The visitors countered to send Craig Bryson through on goal, and he made no mistake as he coolly chipped over Alnwick.
The final whistle brought about a familiar feeling that the Addicks had suffered another defeat that was not for the want of trying.
But Charlton just could not do enough to dent Derby's defence on another frustrating afternoon in SE7.
Charlton: Alnwick; Wilson (Sordell 85), Wiggins, Morrison, Dervite; Green (Harriott 65), Pritchard (Church 65), Stephens, Cousins, Stewart; Kermorgant.
Subs (not used): Pope, Evina,Wood, Solly.
Booked: Stephens 54 (foul on Forsyth), Kermorgant 80 (dissent).
Derby: Grant; Wisdom, Forsyth, Keogh, Buxton, Eustace, Bryson, Hendrick, Ward (Keane 88), Dawkins (Russell 74), Martin (Sammon 85).
Subs (not used): Legzdins (GK), Bennett, Cisse, Davies.
Booked: Keogh 20 (foul on Kermorgant).
Goals: Ward 32, Bryson 87.
Referee: Mr A Davies.