It came as the Knights pressured in the final 15 minutes after a Shaun Kenny-Dowall try set up a nervous finish.
The Raiders have uncovered a cult hero in John Bateman, who looks set to also become a bonafide NRL star with another massive night – this time in the second row to highlight his versatility.
He finished with 201 metres and 36 tackles, and showed some footwork that Knights five-eighth Kalyn Ponga is normally known for.
Williams took full advantage of Aidan Sezer’s injury (oblique), with his kicking game on song and he also showed his ability to read the game.
He almost got on the end of a Josh Hodgson grubber, only for the video referee to controversially rule there was no downward pressure.
But he got his four-pointer later in the first half with a nice show-and-go that opened a gaping hole in front for him to score.
That sent the Raiders into the sheds leading 12-4 at half-time after they also opened the scoring.
It could’ve been lock Ryan Sutton who opened the scoring, but his lost control trying to put the ball down in his run-on debut.
He got through plenty of tackling (35) and looked right at home in the middle.
The Green Machine did get on the board first though with another Hodgson grubber perfectly placed for a charging Charnze Nicoll-Klokstad to score his maiden Canberra touchdown.
That came off the back of a brilliant Bateman run, where he danced like Ponga.
If it wasn’t for one defensive lapse, they could’ve held the Knights scoreless in the opening 40.
But Knights centre Jesse Ramien split the Raiders line and he scooted 40 metres to score in the corner.
Fellow Newcastle recruit David Klemmer was his usual metre-eating self (141m), but his impact was diminished in the second half.
Raiders five-eighth Jack Wighton had a mixed kicking game – two out on the full, but he almost created a try with a bomb that Knights fullback Kurt Mann couldn’t handle.
It was also his charge down that led to Williams’ try.
With torrential rain and lightning greeting the second half, the game became a bit of an arm wrestle – one which the Raiders were winning.
Knights coach Nathan Brown might’ve said it wouldn’t happen for weeks, but he decided to throw Ponga to fullback halfway through the second half.
But it wasn’t an auspicious return – he lost the ball with his first kick return.
That led to Nicoll-Klokstad stepping through for his second – and his fourth double in just 10 NRL games.
While that should’ve led to a comfortable Raiders finish, another defensive lapse allowed Kenny-Dowall to make it a one-try game with 15 minutes remaining.
Ponga might attract some attention for his tackle around Nicoll-Klokstad’s throat.
A few Edrick Lee errors, coming up against his former club, eased the pressure on the Green Machine in the dying minutes.
The Raiders head to Townsville next week to play the North Queensland Cowboys on Saturday, while the Knights host St George Illawarra on Sunday.
AT A GLANCE
CANBERRA RAIDERS 17 (Charnze Nicoll-Klokstad 2, Sam Williams tries; Jarrod Croker 2 goals; Williams field goal) bt NEWCASTLE KNIGHTS 10 (Jesse Ramien, Shaun Kenny-Dowall tries, Kalyn Ponga goal) at Canberra Stadium. Referees: Jon Stone, Tim Roby. Crowd: 10,585.
David Polkinghorne covers the Canberra Raiders, local rugby league, Canberra Cavalry, racing and cycling, along with every other sport, for The Canberra Times.