Mystery Smell

There is an odd smell in my house. My housemates and I can't seem to find where it is coming from and it is driving us all crazy. It kind of smells like something is dead and is decomposing. It could also be food that has gone bad and is rotting away. I can't quite put my finger on it. It's gross though. The smell also seems to travel from room to room and linger there for awhile like some sort of spirit that haunts the house. Pretty creepy, huh? I wish I had a dog or something because I'm sure the dog would be able to sniff it out in no time. So, in the meantime I'm going to continue to search the house for this mysterious smell and if I find out what it is I will report back to you.