Silvertooth: Book 3 by Paul Van Loon
When a mysterious stranger suddenly turns up claiming to be Alfie's guardian, Alfie's happy days living with Tim's family are over. Soon, Alfie's trapped in a cage with a grouchy vampire and a mysterious creature called a scoffle. He's been 'collected' by werewolf hunter, Sebarino Silvertooth, who's captured extraordinary creatures in order to sell them to researchers. Can Tim and his parents, with the help of Grandpa Werewolf and Noura help Alfie escape before he ends up in a lab...