It took the Bluebirds just three minutes to take the lead. An effort from the in-form Craig Noone was palmed around the post by Ben Hamer and the resulting corner was flicked in at the near post by the head of Helguson for his sixth of the season.
A flowing move then saw Cardiff come close to doubling their lead but Noone's shot came off Joe Mason and went wide.
The former Plymouth striker would get himself on the scoresheet in the 24th minute though to seemingly put Cardiff in control, lashing the ball home from close range after defender Ben Turner rattled the crossbar.
But the home side pulled a goal back 15 minutes later with their first shot on target. Cardiff keeper David Marshall dropped a long ball and Johnnie Jackson had the simple task of putting the ball in the empty net.
Jackson then grabbed his second on the stroke of half-time to turn the game on its head. Turner did well to clear Rob Hulse's header off the line and when the corner came in Jackson rose unchallenged to nod the ball in from six yards out.
And the turnaround was complete nine minutes after the break when Dale Stephens' 40-yard free-kick from the left hand side flew over the head of Marshall.
The sixth goal of an incredible match followed just four minutes later when Danny Haynes, recalled to the side along with Stephens, headed home from close range.
Cardiff's away record has been in stark contrast to their superb home form and they conceded their 18th away goal of the season when Hulse rose unmarked to nod home his second in two games from Salim Kerkar's cross to make it 5-2 after 65 minutes.
Malky Mackay's shellshocked side failed to create any chances of note in the final 25 minutes but rallied as the game reached stoppage time.
First Noone rounded Hamer to score for the third game running and then four minutes into added time substitute Aron Gunnarsson netted to set up a thrilling finale. Incredibly Noone had a chance to snatch a point in the dying seconds but his effort flew just over.