As the Saints had in the Salford fog, the Under-18s made some early forward dominance count and blindside Simon Uzokwe was the man to benefit, crashing through a wall of Sale defenders from close range.
The score came after just three minutes, but it was the hosts who then stole the initiative and skipper Sam James got the Sharks underway with a penalty after an earlier effort had gone astray.
They would stay on the front foot at the start of the second 35 as well and it took little over a minute for them to capture the lead for the first time thanks to James' finish on the right - a score he converted himself.
That gave Sale a slender 10-7 lead that would remain unchanged until the hour - despite both sides being reduced to 14 men at one stage. Then next move came from the visitors and Jack Allcock, who collected a Lewis cross kick to dot down.
Lewis converted, but his work was not done yet. Again the Sharks hit back through George Beal, but with the conversion crucially missed any Saints score would be good enough for the win and Lewis nervelessly bisected the uprights with the final three-pointer just minutes from time.
3mins SAINTS Try Uzokwe Con Shepherd 0-7
24mins SHARKS Miss pen Mitchell
26mins SHARKS Pen James 3-7
HALF-TIME SHARKS 3 SAINTS 7
41mins SHARKS Try & Con James 10-7
48mins SAINTS Yellow Wacokecoke
51mins SHARKS Yellow Neild
60mins SAINTS Try Allcock Con Lewis 10-14
66mins SHARKS Try Beal 15-14
67mins SAINTS Pen Lewis 15-17
FULL-TIME SHARKS 15 SAINTS 17