See match highlights as a rocket from Inverness' Williams defeats Aberdeen
Video highlights of the SPFL Premiership game between Aberdeen and Inverness.
Inverness earned just a second Premiership win under boss John Hughes as they overcame Aberdeen at Pittodrie.
The 1-0 loss ended a four-game winning run for the Dons, who had also won eight of their last nine, but Motherwell's defeat to Celtic meant they remained second.
An early Barry Robson corner caused confusion in the Inverness area before goalkeeper Dean Brill took control of the situation.
On a rare foray into Dons territory, Aaron Doran's cross from the right found Williams in space at the back post and he blasted home off the underside of the bar.
Billy McKay had been quiet in the first half, but after the break he had an eight-yard shot blocked and then raced forward on the counter-attack, with only a muscular challenge from Anderson shutting him out.
Aberdeen became increasingly desperate in their bid for a goal and were almost caught out at the other end.
Graeme Shinnie's challenge caught Flood unawares, and after exchanging passes with McKay, he fired in a shot, only to see his effort come back off the bar.