The Kangaroos started well and never dropped their heads but the Saints always had Saturday's match in their keeping after halftime, going on to win 15.13 (103) to 10.5 (65).
Young gun Darcy Wilson put in another eye-catching display, picking up 21 disposals and booting three goals.
Darcy Wilson tries to break a tackle in the win over North Melbourne. (Joel Carrett/AAP PHOTOS)
The bottom-placed Roos made a bright start to the game, booting three successive goals midway through the opening term to gain an early 12-point advantage.
The third of those goals came when St Kilda defender Webster's kick across goal was intercepted by North youngster Tom Powell.
Webster predictably earned the opprobrium of the Kangaroos fans, having been suspended for seven weeks for a late, high shot on North co-captain Jy Simpkin in a pre-season game.
Simpkin was the first Kangaroo to get in Webster's face on Saturday after the error.
The Saints then wrested control of the game, kicking six successive goals either side of the quarter-time break, a run finally broken late in the second term by Cam Zurhaar.
Small forward Paul Curtis kicked the first goal of the third term to trim the margin to 21 points, but the Kangaroos never got closer than that as the likes of Jack Sinclair, Nasiah Wanganeen-Milera and and Marcus Windhager kept St Kilda in control.
St Kilda coach Ross Lyon said Webster coped well with what could have been a difficult return to action.
"He just texted me and said 'thanks for backing me in' and I said 'no worries, we trust your character," said Lyon.
"Other than that, I let him go.
"He worked with (assistant coach) Corey Enright and was pretty calm and composed.
" ... there was a little bit of emotion there at the end and I get it.
"No-one likes to see their teammates get hurt."
Playing his first game since breaking his collarbone in round two, former Kangaroo Wood was among the Saints' best.
Former Roo Mason Wood (L) celebrates a goal on return with Jimmy Webster. (Joel Carrett/AAP PHOTOS)
North Melbourne's better players included young guns Colby McKercher, George Wardlaw and Harry Sheezel.
Fullback Aidan Corr comprehensively won his battle with St Kilda spearhead Max King.
"There were some pleasing signs with the side today," said North Melbourne coach Alastair Clarkson.
"If we continue to play with that type of endeavour then we feel like a win isn't too far away for us.
"We just have to do it consistently."
North veteran Liam Shiels will face scrutiny from the match review officer for his high bump on first-year Saint Angus Hastie in the opening quarter.
Hastie was able to continue before being subbed out in the third term in a tactical move.
The Saints improved their win-loss record to 3-5 ahead of a round-nine clash against Hawthorn in Launceston, where they expect to welcome back exciting small forward Liam Henry from a hamstring injury.
The Roos' next match is against Gold Coast in Darwin.
