Transfusion

When Derek's best friend, Harper, comes back from vacation, she's different - like "growing scales" different. Experimented on by dark Fae, she's going dragon, and she's going to need venom to survive.

Harper, who thinks anything is better than that kind of painful death, enters into a contract with the Queen of the Fae - she'll train and fight for their army in return for the venom she needs. Derek thinks that arrangement sucks. He sets out to find the venom on his own, with the help of a Fae girl that just won't go away.

When they discover the Queen has joined the dark side and is not only holding Harper prisoner, but planning an invasion of her own city, Derek might have to change his quest from a search to a rescue. Venom won't do much good if Harper's already dead. Too bad saving her from the invaders may mean they miss their one shot at getting the venom before the dragon thing kills her.