A few items that have caused intermediate drain problems, trunk light on, cigarette lighter defective or has something stuck in it, defective starter solenoid, a remote amp that fails to turn off, defective ignition key not turning off all the circuits, stuck relay, alternator problems. Have you added any additional 12V items to the car that may be the problem?
A 4-hour time between engine off and drain is not that long. Is the alternator charging the battery fully? If the battery is good and fully charged, this is a considerable drain, at least 10 amps. How long has this being going on? If just starting and you have a very old battery, might be the battery is dieing.
Is the battery really dead and it is not just a problem with the battery cables or starter?
When you turn off the engine, check to make sure all electrical items are off. Pickup a cheap amp/volt meter. With this you can measure alternator function at battery (around 13-14.5v), battery voltage when engine off (12.8v is about 100% charge). By placing the amp meter between the positive terminal you can see if there is a drain, then start pulling fuses to narrow down the circuit.