It's difficult to give you a good answer.....It all depens on what you have done in the game before you go talk to Weston in the chapter. Agatha Christi's Evil Under the Sun is a very liniar game in witch you must do all the right things in the right order and also do all the taking in the right order. Perhaps my very detailed walkthrough can help you out here. But the walkthrough is Dutch, so I will understand if it's of no use to you.
Marinus_Louis