Former England and Manchester United midfielder Paul was in the stands as the on-loan Hull player scored two long-range efforts for the visitors, one in each half.
Play-off chasing Derby were 1-0 up, 3-1 down and 4-3 behind in an amazing game which also saw Huddersfield have three goals ruled out.
Ince crashed home a stunning 25-yard drive on 16 minutes seconds after seeing a free-kick from similar distance saved.
Derby lost Craig Bryson to injury early on and then Zak Whitbread also went off on 27 minutes.
After that Huddersfield, seeking back-to-back home wins against play-off contenders after beating Ipswich last time out, stepped up a gear.
Nahki Wells and Ishmael Miller went close before three goals in seven minutes left Derby shell-shocked.
There was controversy about Huddersfield’s first on 38 minutes when Oscar Gobern appeared to handle Conor Coady’s ball into the box.
Everybody except Gobern seemed to stop for a flag or whistle but neither came and he hooked in from close range.
Gobern, out of contract at the end of the season, last scored for Huddersfield in January 2012.
A Mark Hudson header from a Reece James corner deflected into the net off a Derby defender on 41 minutes.
Reece James, on-loan from Manchester United, then scored his first goal for the Terriers straight from a corner.
He whipped in an effort from the right in first-half injury time and it went in after Derby keeper Lee Grant came for but missed the ball.
Derby came out for the second half on fire and were quickly level when first Simon Dawkins and then Jesse Lingard scored.
Substitute Dawkins fired in from a Stephen Warnock cross on 52 minutes while Lingard struck from outside the box after Dawkins initially tried to shoot.
Midfielder Lingard, like James, is on loan from Manchester United but unlike the Town man has just signed new a two-year contract at Old Trafford.
Huddersfield, pegged back at 3-3, would not give up and were in front again when Wells had a shot deflected in.
He had already had a goal ruled on 57 minutes when he followed up with an effort off which looped into the net off a Derby defender after Ishmael Miller was denied.
It was end-to-end action and Ince scored his second – again from distance – after good work by Darren Bent to make it 4-4 on 79 minutes.
Miller had two goals ruled out, one for a foul on Grant and the other, in stoppage time, for offside.
Also in injury time Hudson headed wide from a Jacob Butterfield cross while Johnny Russell nearly had the last word with a free-kick which just went over.
A point will help cement Derby’s play-off position. Huddersfield, who are already safe, are now unbeaten in five matches.