Oakleaf bearers. John Flanagan. 2009.

Just as spring approaches and Will and Evanlyn can finally escape Skandia, Evanlyn is carried off by mysterious horsemen. Will sets out after them, but one boy against six fierce Temujai warriors is impossible odds - even for a Ranger’s apprentice. Halt and Horace arrive just in time . But there’s no time to celebrate the reunion as Halt realises these Temujai are only scouts for a massive invasion force. The Araluans must work together with the Skandians to defeat the invaders - if the Oberjarl will accept their help.