"What house are your brothers in?" asked Harry.
"Gryffindor," said Ron. Gloom seemed to be settling on him again. "Mom and Dad were in it, too. I don't know what they'll say if I'm not. I don't suppose Ravenclaw would be too bad, but imagine if they put me in Slytherin."
"That's the house Vol-, I mean, You-Know-Who was in?"
(Harry Potter and the Sorcerer's Stone)
When if clause becomes the complement of imagine, is the clause supposed to be interpreted as imagine the assumed situation that they put me in Slytherin?