I found
this online:
24— ‘they talked to the casino about what had happened’
‘Talk’ is a prepositional verb. When it has an object, the preposition ‘to’ must be put between the object and the verb. In the text,
the object is the noun clause ‘what happened,’ but the verb can also have a noun phrase as its object as in “He wanted to talk to a good lawyer.”
about what had happened
in what appears
Do you see any similarities?
Can we say "what appears to be a gangland killing" is the object of the preposition "in"?
Look
here too.
And
here:
In class today, we talked about what Mr. Duncan expects in our next research essay.
About = preposition;
what Mr. Duncan expects in our next research essay = noun clause or the
object of the preposition.