We’ve been working for so many years that we should be able to smell a trap, even if our enthusiasm is hard to kill.

No.
It seems we’re not.
So, for the nth time: if a client call you to shoot on location (especially in a house) without knowing the subject, the place and having absolutely no idea of what you’re going to find there and with any clear directive, well, say “No, thank you”.
The risk is to loose a client not because of your own fault: getting three or four good shots is an impossible goal in that situation.