The Kindness of Strangers
In The Kindness of Strangers , Finna first appears watching Merlin as he picks flowers in the forest for Guinevere at Arthur's order. She tells him she has been told to warn him about the great battle. They are interrupted and Merlin promises to seek her out.
She is later seen using a crow to deliver a message and we hear her use Morgana's name making us assume Gaius was right, having told Merlin not to trust her (it was later revealed it was to send a message to where Alator is being held). He later visits her despite Gaius' protests.
They are then ambushed by Arthur's knights being led by Mordred and are forced to separate despite Finna's protests. Later she is seen being tracked by Arthur's knights, Morgana's forces and Merlin; The knights because of Arthur's orders, Morgana's forces because she is determined to know who Emrys is, after having failed to extract the necessary information from Alator, and Merlin to finish their discussion.
When Merlin eventually tracks her down after being delayed by the knights, they are attacked by several of Morgana's men and during the ensuing fight both are forced to use magic and Merlin is injured by an arrow from a crossbow. They then journey to a tower as Morgana notices that one of them was injured and the evil forces follow the same path Finna and Merlin take.
Finna assists Merlin in climbing the tower and informs him not to trust Mordred and gives him a box. Morgana's forces then enter the building, and although Merlin tries to stay and help her, she tells him it is her destiny to serve him, and tells him that it has been a privilege to have known him(Emrys). She then asks for Merlin's sword.
Merlin then goes to the roof, following Finna's instruction. Morgana soon comes across Finna who bravely points her sword at Morgana. Morgana then demands to know who Emrys is. Finna defies Morgana and refuses before stabbing herself with Merlin's sword; ending her life in a courageous manner, standing up for what she believed in.