It didn't start well for Boro, conceding a penalty after just three minutes with Remi Oudin beating Tom Dawson from the spot after Dael Fry had been adjudged to have fouled Youness Aouladzian - it was a decision that might not have been given in the English game, but this is European football and this is different.
The home side kept up the pressure and Dawson had to be alert when Aouladzian was set up Aly Ndom.
But it didn't take long for the hosts to find the net again.
With just 12 minutes played Amadou Sylla delivered a fine cross to pick out Andrew Jung who headed home.
It was the ideal start for Reims coach Franck Chalencon who had said before the game he didn't know what to expect and felt the game would be controlled by the side who played their own game rather than take took much notice of the opposition.
His side had taken his preparations to heart and they might have gone three up when Jung, set up Ndom, saw a close range shot saved by Dawson.
Boro had set up with an attack-minded side but had been rocked by the fast start and took a while to settle.
Their first chance came just short of the half hour mark when Harry Chapman was just off target with goalkeeper Nicolas Lemaitre beaten.
At this stage Boro, though two down, were back in the game and at least giving an account of themselves.
It was Chapman again who caused a few problems in the early exchanges of the second half, just seven minutes into it and he wasn't far off target.
Mitchell Curry was the man on target with 58 minutes played, his fifth goal in four games getting Boro right back in it.
The response from Stade de Reims was instantaneous and devastating as 40 seconds after the restart Oudin scored his second of the night with a sumptuous volley, Andrea Marques made it 3-1 on the hour with a powerful header and less than a minute later Sylla made it five when cutting in from the wing to crack home.
The game had taken a life of its own. There had been little sign of a goal flurry with such intensity and Oudin almost made it six.
But it was Boro back on the scoresheet as Callum Cooke reduced the arrears with a neat finish with 23 minutes of an astonishing second half played.
With 15 minutes remaining it was Cooke again, this time from the penalty spot, following another decision from the Belgian referee which on another night might not have been given.
It set up a grandstand finish and in the final minute of normal time Chapman forced a full-length save from Lemaitre with a low shot.
The Riverside has witnessed two never to be forgotten comebacks on European nights before, from positions far worse than this.
This tie is far from over.
Stade De Reims: Lemaitre. Marques, Rousseau, Vallier (Petel 73), Favre (Hajjem 70), Oudin, Aouladzian (Nejjari 83), Ndom (Capt.), Sylla, Jung, Navet. Subs: Ripert (gk); Francoise, Boubidar, Vandenameele.
Boro: Dawson; Fry, McGinley, McGoldrick (Hegarty 70), Elsdon, Cooke, Johnson, Pattison, Mondal, Chapman, Curry (Tavernier 61). Subs: James (gk); Jardine, Cook, Reading, Liddle.
Referee Vertenten Bart (Belgium)
Fry 3, Curry 65, Johnson 77