Complex sentence: He showed her a file the Talamasca (an order that investigates and documents supernatural things) had on her, they knew of her ability to see spirits and wanted her to be part of the order.
Split into simpler sentences: He showed her a file the Talamasca (an order that investigates and documents supernatural things) had on her. Apparently they knew of her ability to see spirits and wanted her to be part of the order.