it may happen on a morning that you wake up home alone. this could be normal, depending on your situation, but this morning will be different. while your environment will seem exactly the same, you'll notice that everything is quieter than normal. if you go outside, you will notice a distinct lack of anything, like birds, insects... or people. as far as you travel, you will not encounter another sentient human being. the entire world will be intact. but empty except for yourself.
there are currently over 100,000 missing persons cases in the US. some are just normal cases of kidnapping or a murder, but in others, the disappearance cannot be explained and no remains of the person are ever located.