How on earth did Neuville not suspect The Father?

After the discovery of his formerly hired killers' bodies, he knows something's not right.

He starts suspecting the husband. OK. He finds the e-mail and sees that the death of Margot was a hoax.

So two questions: a) Where is she? b) Who organised the hoax?

He 'returns' to that night she died: the husband was found unconscious - well, OK, maybe that was staged as well. But who knew HOW the Margot's murder was supposed to look? WHO knew of the plan to kill her, who had the brains, ability and time to carry out such a smart counter-plan?

A doctor husband, who knew nothing about Neuville's ways, or a dirty cop father who stayed close to Neuville?

It is truly strange that Neuville's gang wasn't after the father after they found out Margot was alive.