Watford are trailing to Jeremie Aliadiere's second goal for Wolves at the break.
Following a quiet opening, it was the hosts who took the initiative and Colin Cameron just failed to find the target with a left foot effort that perhaps he should have left for an unmarked Lee Naylor.
At the other end, a miscued clearance by Wolves goalkeeper Stefan Postma under pressure from Marlon King gave Darius Henderson sight of an open goal, but his header from long range, although on target, just lacked sufficient power to embarrass a back pedaling keeper.
The home side took the lead in the 17th minute when a defence splitting pass by Tomasz Frankowski found Aliadiere, and the on loan Arsenal man forced the ball low past an onrushing Foster.
Frankowski
As half time approached it was Watford who were applying the pressure on the home goal with a number of Ashley Young corners.
However, manager, Aidy Boothroyd has much to do in his half time team talk if the Golden Boys are not to suffer a third defeat in four games in the Molineux sunshine.