Welling were sunk by a late wonder strike from former Welling man Alfie Pavey as they were cruelly denied having come back from two goals behind.
Just as they did on Saturday Welling started poorly and they were behind inside three minutes.
A low Ryan Hayes cross was met by Andy Pugh who had the freedom of Welling to stroke the ball past Ryan Sandford from close range.
The same combination nearly saw Dartford double the lead but this time Pugh headed wide from a Hayes cross.
Slowly Welling got into the game and Bradley Goldberg saw a shot turned around the post by Darts keeper Deren Ibrahim before he did the same to a Olu Durojaiye long-range shot.
Christian Nanetti then hit the post after his shot from a mazy run deflected off of Tom Bonner and onto the post.
Jack Parkinson then should have done better from a Monakana corner but headed wide when unmarked.
Welling finished the half strongly but after good work from Nanetti his cut back to Goldberg saw the striker force a super save from Ibrahim.
Welling replaced the injured Bradley Goldberg with Tom Bradbrook at the break. He almost made an immediate impact after latching onto a ball over the top he smashed his effort straight at Ibrahim.
As it was Dartford went further ahead in the 55th minute . Hayes and Pugh again combining as Pugh swept home an almost identical goal to his first.
Dartford almost put the game beyond Welling when Danny Mills beat the offside trap to lob Sandford, with Mills off celebrating, the striker had to stop as the ball bounced off the post and was cleared.
Andy Pugh then almost got his hat trick just failing to turn a Nathan Collier’s cross in as Dartford looked to be cruising.
Perhaps buoyed by these misses Welling started to show some character. Ian Gayle was guilty of missing a sitter Derren Ibrahim spilled Callum Driver’s long-range shot and with Gayle looking certain to score the rebound he side footed over the bar with the goal at his mercy.
With 13 minutes to go, Welling got back in the game. After Nanetti was fouled just outside the box, Callum Driver curled a superb free kick into the top corner.
With Welling throwing everything at Dartford, the Wings won a penalty. Tom Bradbrook was fouled by a combination of Tom Bonner and Elliott Bradbrook Monakana cooly slotted the penalty past Ibrahaim despite the keeper being a long way off his line when the penalty was taken.
However in a cruel twist, Dartford won the game in the 2nd minute of injury time. Welling fouled to clear a long ball into the area and the ball fell kindly to Pavey who
volleyed superbly from 20 yards out into the corner. It left Welling heartbroken and licking there wounds in mid table after a wretched run of results in December.
The return fixture is next with the game at Dartford a 3pm Kick off on New Years Day.
Welling: Sandford, Driver, Jefford, Durojjaiye, Gayle, Parkinson, Monakana, Dymond, Romain, Goldberg (Bradbrook 46mins), Nanetti. Subs not used: Jebb, Francis, Phipps, Johnson.