When recent murders indicate the return of mythological creatures, a dismissed errant detective finds his estranged-and-murderous wife coming for him, out for revenge.

The initial descriptions are not of the inciting incident - as DPG wrote there's no causal connection between that and his ex wife.
However, you seem to end the logline on an inciting incident - "...his estranged-and-murderous wife coming for him..." what must he do now as a result of this?

What's the cause-and effect relationship between the return of the mythological creatures and a ?estranged wife out for revenge? ?(And exactly what kind of revenge? ?Unfriending him on Facebook? ?Murder? ?Be specific.) ? What's the inciting incident for a plot here?

And what is the detective's objective goal as a result of his estranged wife?wanting revenge?