Arsenal squandered a two-goal lead in Germany as Schalke denied Arsene Wenger victory on his return from a touchline ban as the two sides recorded a 2-2 Champions League draw.
Having held off Schalke's intense early pressure, Theo Walcott netted his 50th goal for Arsenal against the run of play in the 18th minute after Olivier Giroud was dispossessed in the box. The France international got in on the action eight minutes later with a superb diving header, but Klaas-Jan Huntelaar reduced the deficit in first-half stoppage time.
Arsenal were pinned back as Schalke poured forward in search of an equaliser and, despite goalkeeper Vito Mannone's best efforts, it came when Jefferson Farfan fired home via a Thomas Vermaelen deflection.
Laurent Koscielny came into the starting line-up in his place and Walcott overcame illness to replace the injured Aaron Ramsey, while Schalke named an unchanged side.
Arsenal were struggling to get the ball out of their half and somewhat fortunate not to go behind when Lukas Podolski was caught in possession and Schalke broke, with Mannone saving superbly to deny Ibrahim Afellay at his near post.
The Royal Blues' pressure did not relent and Benedikt Howedes headed over a Farfan corner as they continued to press for an early opener that, rather surprisingly, came at the other end.
Roman Neustadter's poor back header put through Giroud through on goal and, when the dallying Frenchman was dispossessed by Howedes, Walcott collected the ball and went on to slot home unopposed.
Atsuto Uchida was forced off injured so Marco Hoger slotted in at right-back and soon found himself caught out by Podolski. The Germany international turned the substitute and whipped in a low cross that Giroud met with a superb diving header in the 26th minute.
Schalke looked shellshocked and Fuchs was booked, before Giroud headed straight at goalkeeper Lars Unnerstall. But, just as Arsenal looked set to go into half-time with a two-goal cushion, neat interplay from the hosts put Huntelaar through and he lashed home in stoppage time .
Mannone did brilliantly to palm away a driven Lewis Holtby effort deep into the second half, before stopping a long-range Afellay strike. The Italian goalkeeper could not keep Schalke at bay for much longer, though, and when Farfan collected the ball on the right-hand side of the box he fired home via a deflection off Vermaelen.