I was out of town for two weeks, came back and the car won’t start. I put a battery charger on it for about an hour, nothing. Now have another car running with jumper cables, and it still won’t start. Is there some thing I’ve missed? An interlock of some kind, or a magic word to chant?

 

Might just be the battery is toast,an hour on the charger may not have been enough especially if it's dead because you left lights on or something.
That said I've seen this scenario simply because a little corrosion was on the terminals even with a jump,first thing I'd do is pull the cables off and clean the battery terminals with a wire brush and also clean the terminal ends really well. If there is a lot of corrosion on them some baking soda and water paste will help a lot before the wire brush,slather it on and let sit for 15-20 minutes and then hose it off with water. Make sure the terminals and cables are shiny clean and nice and tight when you put them back on.

 

As suggested, put charger back onto battery overnight.
Power is going to PCM, BCM (Body Control Module), and Radio.
If current draw is measured, ammeter between battery cable and battery post, should be less than 0.1 amp or less.

 

are you getting any lights or other things coming on when you have the jumpers on? if you have dash lights when jumped with another battery then it may be battery is toast. if the battery is toast and completely discharged it will not take a charge and the jump would not allow the amps needed to start or even get engine to turn over.