Games between these two have tended to finish either 2-2 or 3-2 in the last season and a half, so goals were expected.
The first half was a bitter disappointment, though. Dundee started strongly, Jordan McGhee had a chance well saved, but Kilmarnock were well off the pace and struggled to adapt to their new 3-4-3 system.
Cameron and Simon Murray went close too, meaning Tony Docherty's side might have felt more aggrieved to go in goalless.
Whatever McInnes said at half-time seemed to work - initially. Gary Mackay-Steven had a shot well saved before blazing over from near the penalty spot.
Dundee made them pay for that profligacy, as Robbie Deas failed to clear a cutback and teed up Cameron perfectly, who finished well from 10 yards out.
Within 10 minutes, Kilmarnock had their equaliser. Wales, who scored a hat-trick in midweek for the reserves, entered the fray and soon lashed brilliantly into the top corner after Brad Lyons got down the left well and found Vassell, who laid off to the 19-year-old.
The hosts should have won it from there. Marley Watkins went one-on-one but Jon McCracken saved, and Lyons scuffed his follow-up.
Wales could have scored with the final play of the game, but McCracken made another fantastic save.