Charlton's U21s exited the Premier League Cup following a late 3-2 defeat against Watford at The Orbital Fasteners Stadium on Monday night.
Following a goalless first half, Amin Nabizada gave the hosts the lead on 64 minutes, firing past George Hardy.
The young Addicks responded just eight minutes later through Kaheim Dixon following a superb run from Ibrahim Fullah down the left-hand side.
Zach Mitchell gave Charlton the with just nine minutes remaining, volleying home on the turn.
The Hornets were given a golden opportunity to restore parity in the final minute of regular time and Jonathan Lawson made no mistake, converting his spot-kick.
Further drama would follow as Tobi Akinyimika struck a 92nd-minute winner to book Watford's place in the last eight of the Premier League Cup.
Chris Lock's side are next in action on Friday when they host Millwall at Sparrows Lane (KO 1.30pm GMT).
**Charlton:** Hardy; Laqeretabua, Mitchell, Ewens-Findlay, Brown; Gough (c), Enslin, Fullah (McMillan 80); Dixon, Lock (Amissah 80), Reid (Safa 90)
**Subs (not used):** Williams, Kuczynski
**Goals:** Dixon 72, Mitchell 81
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