It has always been a possibility that Madeleine is dead and possibly killed by an intruder who attempted to shut her up if she woke and was about to start screaming. But most of us prefer to hope that she is still alive, so we tend not to think about it.
On the other hand, No McCann Sceptic is ever going to entertain the idea that an intruder could have killed Madeleine because this might exonerate The McCanns.
Now that this possibility has been raised we are attempting to discuss it, hopefully without too much abuse.
So why don't the sceptics come up with reasons for why this unlikely?
Alright, in this particular scenario involving a serial offender, I find it unlikely that he would change his MO so dramatically, that he would leave children able to identify him alive (not the twins, the other victims) yet take a corpse. That he would not leave any sign of being in the apartment, not just no sign of a break in but no hair or fingerprint or DNA sample.
Given the the lack of evidence, he would either have had to have worn gloves/protective clothings, or have taken the time to clean up. If we're taking the checks on the children as fact, there's no time for a clean up operation, if gloves, no need to remove a body.
Plus everything that Serendipity just said.