Recently we have had a neighborhood cat adopt us. She stayed on our back porch all winter and lo and behold she had kittens in the bed we made for her back there! :) However about 2 weeks after she had them, she moved them off the back porch. :( Now we cannot find them. Today we heard them and it sounded like they were in the heating vents of the house. We went down to the basement of our house and found one lone kitten. Now we have NO idea where she came from or where the other kittens are. They are only about four weeks old and I am wondering how to care for this one until we can find the other ones and momma cat. Any suggestions?

First thing's 1st and that is food. It likely needs milk or formula, and soon. You can find this at any pet store or going to your local vet clinic would be a better bet. You will likely need an eyedropper to get anything into it's tiny mouth. Will likely need to be feed a few times a day at least, just like a baby. It would be far to young for any type of "cat food" so do not waste your money there. The Humane Society should be able to give you good advice on how to further care for the kitten, as well as lure the other's out. I would start by leaving food in the basement where the kitten appeared. It may be enough to draw out Mom & family. It may be best. If you are willing, to give the cats & mom a small room in your home while they are young to ensure their well being (like a closet would be fine) Young kittens are prey just as much as a baby raccoon or baby bird would be, and are not very safe outdoors. It is likely that Mom moved the kittens off the back porch as it was not protected enough from predators. Hope that helps.