It all started out rather beautifully.
Legia Warsaw, the first Polish team to reach the Champions League group stages in two decades, unfurled an incredible tifo before kickoff to mark their side's return to the summit of the European game, at home against Borussia Dortmund.
Then followed some mighty fine goals by the German visitors. Dortmund, the 2013 finalists, have packed their squad with some remarkable young talent, including Christian Pulisic, who was making his first start of the season and his Champions League debut.
But things soon turned ugly in Warsaw as the match quickly turned into a rout on the field. The score was 3-0 by the 17th minute, and Dortmund would eventually win 6-0. At some point before half-time, a band of balaclava-clad Legia hooligans tried to invade the Dortmund section of the stands.
Judging from the above footage, the ultras were rebuffed by the stewards and so set about dousing them with pepper spray; one steward taking cover was kicked in the back. The confrontation seems to have been contained to the Legia section, though, and to have dissipated in fairly short order.
Poland has a long-running problem with hooliganism, and it's now marred the country's return to the Champions League.
A fine from UEFA and possibly further punitive action most likely await.