Simi Sasagi and Hudson Young combined brilliantly in the first half of Saturday's match at Optus Stadium to lift the Raiders to a commanding 24-4 lead by the break.
But three tries in nine minutes catapulted the Rabbitohs back into the contest, reducing the margin to just two points with 23 minutes remaining.
Canberra, riding a four-match losing streak and with their finals hopes already shaky, looked ripe for the picking.
Enter Weekes.
With Canberra camped on their own try-line at the start of their set, Weekes received the ball and embarked on a run that will dominate highlight reels for years.
He broke through two tacklers within his own 10m, shook off another tackler a short time later, before throwing a dummy to fool an opponent.
Still 70m away from scoring, Weekes slipped through a gap and outsprinted two chasers to touch down for a famous solo try.
"He's a freak in regards to some of the line breaks he makes," Raiders coach Ricky Stuart said.
But there was another twist to come.
After Canberra made it 36-22 in the 72nd minute on the back of Ethan Strange's try, the Rabbitohs surged back again.
Tries to Alex Johnston and Jack Wighton reduced the margin to two points, and with 13 seconds remaining Latrell Mitchell launched a bomb in the corner.
Johnston rose the highest, but lost control of the ball as he spun through the air on the landing - with the try-line just one agonising metre away.
"A very good way to describe it - crazy," a relieved Stuart said of the contest.
"It's a credit to the boys how they did hang in there.
"We just needed a win today. It was ugly, but I'd rather win ugly than lose pretty."
The Rabbitohs slipped to a 3-2 record, and will be sweating on the fitness of fullback Jye Gray, who injured the AC joint in his left shoulder in the 13th minute after being crunched to the turf with two tacklers directly on top of him.
The first half was the Sasagi and Young show as the pair tore the Rabbitohs to shreds.
Young scored two tries, while Sasagi produced a series of blistering breaks on the way to two assists.
Raiders winger Savelio Tamale was suffering a case of the fumbles, dropping two high balls to put his team under all sorts of pressure.
But he made up for it in the 28th minute when Mitchell's attempt to flick on a pass before even taking possession went horribly wrong.
Tamale picked up the loose ball at the halfway line before sprinting 50m towards the posts.
Things looked bleak for the Rabbitohs at halftime, but they came back with a bang in the second half to ensure the match went down to the wire.
"If you love your rugby league, you would have been wholly entertained today," Rabbitohs coach Wayne Bennett said.
"Some great tries, great moments, and both teams went pretty hard at it.
"(My players) are never down and out, they've got a great spirit.
"But they just shouldn't give the start away.
"As a great coach once said, they didn't beat us, we just ran out of time, and that's what happened."
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