Harlequins' Heineken Cup hopes were engulfed by a storming defensive display from Connacht as the home side made history with a 9-8 victory in a typically wet and windy Galway.
On a night of upsets in Pool Six, the rain-soaked Sportsground witnessed an intense battle between a home team hunting for their first victory in 15 matches and the Aviva Premiership leaders.
Gloucester did Quins a huge favour in beating table toppers Toulouse, but Conor O'Shea's side blew their chances of winning the group and making sure of a quarter-final place as a nightmare scenario played out.
Niall O'Connor notched three penalty goals to push Connacht into a 9-5 half-time lead, however the hosts failed to take full advantage of a strong wind.
Sam Smith's eighth-minute try showed Harlequins' capabilities with ball in hand, but a single penalty from Nick Evans was all they could muster despite dominating possession and territory after the break.
Irish eyes were smiling on the double as the results in Pool Six sent Connacht's provincial rivals Ulster through to the last eight, in advance of their final pool game against Clermont Auvergne.