I unplugged it, charged it in another room, and installed adb on my mac following the directions here:
http://lifehacker.com/the-easiest-wa...-to-1586992378
It doesn't squeal this time, and adb doesn't work. I tried "adb devices" and got the response "-bash: adb: command not found"
apparently I've got to figure out where these tools were installed... huh?