Can't execute query

SELECT p.*,c.id as cid FROM products_tw p, categories_tw c, products_category_tw as it WHERE it.category in () AND p.id = it.pid AND c.id = it.category AND p.available = '1' AND c.available = '1' GROUP by it.pid ORDER BY p.numbered LIMIT 0, 1

MySQL Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') AND p.id = it.pid AND c.id = it.category AND p.available = '1' AND c.available' at line 1

This script cannot continue, terminating.