Planks in the ceiling

You decide to try flying up to the planks. By willing yourself to push against them you are able to seep through and reform on the other side. Once you are back in human form you find yourself in an empty room with several doors and a large, heavily curtained, window. You go over and open the curtains and are somewhat surprised to find yourself looking out on a modern suburban street, complete with electric streetlights and identical houses.

After a momentary dislocation the thirst comes upon you again and you realize that you must feed soon. You open the window and, almost instinctively, transform your body into a flock of bats and stream out into the night looking for sustenance. A small dog begins to bark at you, it's high pitched yelping assailing your sensitive ears. It takes few of your component bats to end its yelping for good and to slightly dim the damnable blood-thirst. Somehow you know that even killing all the pets in the neighborhood will not bring you satisfaction. Only the blood of a human will do that, although thankfully the yappy dog has given you enough blood to save you from having to end the life of your human victim.

You spread yourself out so as not to raise too much suspicion and in doing so allow yourself to do a thorough search. It is through this tactic that you quickly find a likely 'donor'.