replacement windows leaking at sill....

[js1268]

hey folks,

i'm at a loss, here, and need some help

i had my kitchen windows replaced with vinyl replacement windows by a reputable local contractor.... i told him to hold off on reinstalling the interior casings and stools because i wanted to see if there would be any leaks....and sure enough, after a heavy downpour and wind i noticed that the interior side of the sill felt very damp.... water was getting in under where the exterior frame of the replacement window met the old sill

my question is: Should that area have been sealed with an adhesive or somehow fastened to the sill?

any help would be greatly appreciated....thanks

paul