“You should call Henry.”
The headlights started dimming at 11PM; about 5 miles from home, but only half a mile from Randy's. Randy is a BMW touring bike owner, a close friend, and while he doesn't always have space in his driveway he's usually willing to move one of his kids' cars to give you a spot to park for the night.
I was stopped at a light when I noticed the flashing “something's wrong, knucklehead” indicator, and I went through the list of known electrical issues that could cause a dimming headlight. Starter-switch corrosion is a known issue (the starter switch also contains a normally-closed headlight switch, hitting the starter kills the headlights so there's more juice for starting), so I thumbed that gently a few times to see if it was just a bad contact: no joy. The stoplight was going to turn green soon and in a panic I wiggled the kill-switch, hoping it was a bad contact there. I over-enthusiastically killed the engine (along with any hope I had of a restful sleep that night.) When it was clear there wasn't enough juice to turn the engine over, I pushed the bike onto the sidewalk and ran a more thorough check of vital systems: the hissing battery was basically all I needed to give up hope of getting the bike started again. I called Randy and rolled up to his driveway at 11:23.
Randy had a beer ready as I stripped off the riding leathers, and asked all the pertinent I-own-a-motorcycle questions about switches and components. We stared at the bike for another five minutes before he scratched his head and invoked the name of Henry Devereaux.