Before the body was sent to the crematorium, shilling and Crump filled the casket with animal bones, meat, and a mannequin.
Object of the preposition: genius. The subject of the sentence is called a noun clause. It is a clause because it has its own subject and verb. It is also a dependent clause which cannot stand on its own because of the word that (a relative pronoun) at the beginning of the clause. A noun clause functions as a regular noun in a sentence.
In this example, the noun park is the object of the preposition in. A word cannot be the object of a preposition and the object of a verb, at the same time. So, 'walks' is not a transitive verb in this case. Let's look at some other examples of prepositional phrases.