Karim Adeyemi scored a brilliant solo goal to condemn Chelsea to defeat in their Champions League last-16 first-leg tie at Borussia Dortmund.
The Premier League side rued missed chances as Joao Felix shot over from a good position and then hit the crossbar in the first half.
Reece James also forced two fine saves out of Dortmund goalkeeper Gregor Kobel in the second half as the visitors grew in confidence against the hosts, who were themselves struggling to create many chances.
But Chelsea were undone on the counter midway through the second period when Adeyemi broke from inside his own half following a Chelsea corner, knocked the ball past Kepa Arrizabalaga before slotting into the empty net.
Chelsea, to their credit, pushed for an equaliser and Emre Can swept the ball right off the goalline as Kalidou Koulibaly's deflected strike looks certain to trickle into the net.
Enzo Fernandez thought he'd equalised in the last seconds of stoppage time but his goalbound long-range strike was stopped superbly by Kobel as Dortmund held on.