I didn't think there was a return spring at the pedal, but wasn't sure.
Its one of the following or a combination. The brake cables could be streched. There is an adjustment where the cable splits in front of the rear wheels. The cable could also be frozen (very common in northeastern cars). If its streched too much or frozen, it will need to be replaced.
The cable hooks to a lever in the rear brakes that needs to work freely. The lever works a link between the two brake shoes that needs to be in place.
There is a spring on the cable where it goes through the backing plate that could be broken.