The Virgin of Valkarion by Poul Anderson

The street below was deserted now. They jumped down to it and darted into the shadows on the other side. Slipping along the walls of buildings they followed its twisting length for some time. An occasional cloaked form passed silently by; otherwise there was only the bitter wind echoing hollowly along the tunnel-like streets.

Of a sudden Alfric stiffened. He heard the measured tramp of feet -- a city patrol approaching, just around the next corner. Whirling, he led the way into an alley black as a cave mouth. It was blind, but there was a door at the end, from behind which came the twanging of harps and the thin evil whine of desert flutes. A tavern -- shelter, of a sort --