Dart with no rear brakes?

Drum or disk brakes? With drum brakes you can lose a fair amount of fluid into the drum, absorbed into brake dust, etc., before you see a puddle.

If there's no fluid on the ground and no fluid inside one or both drums, then the missing fluid was either pumped into the other chamber of the master cylinder, or out the back of the master cylinder and into the firewall insulation and carpet – In either case, it means that you need a new master cylinder, which is my first guess at your problem.

They're not expensive. A crappy one from the 'Zone won't last forever, but it will (probably) get the car over to your house.

– Eric