Three stairway lights are controlled by two switches at the top and bottom of stairs. The outlet at the bottom of the stairs is dead. Both switches are wired with two blacks and a red, with commons tied off. The dead outlet does not seem to be at the end of the circuit; the box has a cable running elsewhere (two commons and two hots). No sign of power in or around the outlet box. I have checked all connections except those in the other outlets (high ceiling). What could be going on?
There should be wires bertween the two outlets, check the connections to the working outlet are sound.
Perhaps the dead plug is on a seperate branch circuit from the lights and switches. Check for other dead lights and plugs on other floors. Are you sure this box is part of the light circuit? From your post I assume the lights work. And I dont know what method you used to check for voltage around the plug, but I would recommend a three-pronged plug-in circuit analyzer as well as a non-conductive voltage sensor that lights up when near voltage, if you haven't already have one.