Winfrith "Winnie" Arlin (original surname: "Arm of Lightning") is a witch and a member of Circle Daybreak. She is considered one of the top fighting witches of the organization, and is placed on a team of other top operatives (Keller and Nissa Johnson) in order to find and acquire the third Wild Power: Iliana Dominick, a lost Harman and the prophesied Witch Child.
Winnie is shown as being small and elf-like, similar to the made vampire Poppy North, with "a froth of strawberry curls and a pixie face", as well as "dancing green eyes"; when smiling Winnie is shown to have dimples. When angry, despite her youthful looks, she appears to look older, her face becoming gaunt. She additionally gains a sparkling aura of power, likened by the shapeshifter Keller to a "small but fiery orange comet".
In times of calm or crisis, Winnie is often brave and humorous. She appears to be highly confident, as well as protective of her fellow witches; she shows a deep pride in her Night World heritage, citing her family as being nearly as old as the Harman clan, though less prestigious. However, Winnie also has a quick temper and is described as "emotional" and somewhat excitable, especially when it comes to the witches, quick to turn on the shapeshifter prince Galen Drache when she learns of Grandma Harman's death at the hands of rogue shapeshifters. She additionally has a tendency for blurting information out, often too much too soon, when excited.
She is well versed in creating protective wards, as well as healing and brainwashing, the latter ability shown being done even without verbal spells.
Winnie is sent by Circle Daybreak along with her team to North Carolina, where they had located the potential third Wild Power; they split up inside a shopping mall to locate the girl. She shows light bravado, insisting to Keller when Nissa mentions three Night World operatives looking for Iliana also, that she "can take 'em all on" herself. Keller reprimands the witch for her words, but is in truth amused.
When the two find Iliana at Hallmark, being talked to by the Night World members, she reacts with awe at seeing Iliana, likening her to a legendary savior. She becomes indignant at the thought of Nightpeople talking to the Harman girl and, against Keller's orders, marches into the store. However, the third operative, is in fact a dragon named Azhdeha (the oldest and deadliest type of shapeshifter). Seeing Winnie, Azhdeha uses an immense wave of Power on her, hurling the witch across the room to slam into a wall behind the counter. Fortunately, despite Keller's fears, Winnie is not killed by the blast, rising some minutes after Keller tries to kill the dragon, orange fire ready in the diminutive witch's hands. Intimidated by Keller, Winnie, and the newly arrived Nissa and Galen, the vampires sent by the Night World gather up the wounded Azhdeha and flee, after which the team manages to secure Iliana and depart the mall; the witch defends Iliana's fainting spell, explaining the girl is too pure to handle violence. Winnie further casts a spell on police cars following them to create confusion among the officers and prevent detection.
Once the reality that they have acquired the Witch Child settles in, Winnie reacts jubilantly, but this is short-lived when she sees Keller's anger that Winnie might have been killed. She apologizes, but "smiled timidly[...]afterwards", knowing she isn't in any real trouble and that Keller is angry due to concern over her. Winnie questions who Galen is and, after Keller unleashes her fury at him, Winnie explains to him about Iliana's identity as the Witch Child, and the importance placed on keeping her safe; she additionally expresses confusion over the nature of dragons, assuming Azhdeha "can turn into" a dragon rather than actually being one deep down inside. When Iliana awakens, Winnie happily but formally introduces herself to the girl, but Iliana looks over at Keller and begins inexplicably screaming. Winnie is shocked by the reaction, but her face clears once she understand how Iliana viewed what had happened in the mall. She is further relieved when the silvery-blond girl agrees to go to the safehouse with them on the condition Galen goes with her.
The team brings Iliana to the safehouse, where Winnie sets up minor wards, and they explain Iliana's heritage to her as a Harman and a Wild Power. However, when Winnie excitedly goes on about her role as the Witch Child, who is meant to also marry the son of the First House of Shapeshifters, Iliana reacts with hysteria and refuses to listen. When Grandma Harman arrives to see Iliana, Winnie greets her and introduces her as the Witch Child's "great-great-aunt" and "the Crone of all the Witches". Iliana quips that the eldest Harman "looks it", and Keller gets between the two girls before "Winnie could attack her".
The safehouse comes under attack by the Night World and the recovered Azhdeha; Nissa and Winnie automatically grab Iliana and escape. However, when the house is crushed by the dragon's Power, Iliana shrieks for the pair to return. Unable to deal with the Witch Child's decibles, they make their return and remove Keller, Galen and Grandma Harman from the rubble.
Winnie, Grandma Harman and the matriarch's assistant, Tobias, use magic to heal Keller, bringing her to Iliana's home. Winnie and Nissa update their boss on all that has occurred, though Winnie makes remarks about Keller not thanking them, informing Keller that Iliana had been screaming at them to go back for her, not Galen. At breakfast, she grins and makes jokes about the panther becoming the object of Alex Dominick's attention. She and Nissa also notice Keller acting strangely after her encounter with Galen in the library.
The team brings Iliana to school, Winnie explaining more about the Wild Powers along the way, particularly the time Jez Redfern stopped a train. Once at their destination, the lost Harman makes up a story about the girls and Galen for her class when they arrive, which Winnie reinforces by brainwashing the teacher. The four guard Iliana throughout the day; Winnie is present when Keller accidentally attacks Iliana's friend, Jaime, outside of the music room. The two keep careful watch for the rest of the afternoon, Keller indirectly thanking them.
When Iliana returns from the hospital, she is stricken with a cold; Winnie and Nissa stay in her room to keep guard over the girl. The scrolls of the shapeshifters arrive, but before opening them the team discusses the incident with Jaime nearly being run over by a car; she "glance[s] at him sharply when he" mentions Iliana "having a good mind". To avoid another fight between Keller and the Witch Child, Winnie begins to remove the wards from the box of scrolls, successfully opening it.
However, they receive a call from Circle Daybreak, informing them that Grandma Harman has been murdered in broad daylight by shapeshifters. Winnie reacts to this news first by weeping for her lost Crone, and then with immense fury, rounding on Galen and Keller, accusing the shapeshifters of trying to deceive and destroy the witches; she interprets the killing of the oldest Harman to be as good as a "declaration of war". However, she is interrupted by Iliana, who is upset by the fighting and embraces Winnie, understanding the witch's pain. After a few moments, Winnie calms down, and ultimately she apologizes to Galen for her outburst, stating that if she were the Witch Child she would gladly marry him. Returning to the scrolls, after Galen and Keller finish their narration about the dragons in ancient times, Winnie picks up the story, telling of Hecate Witch-Queen's victory over the shapeshifters along with the witch tribes, the dragon's attempt to obliterate the world, and their subsequent forced dormancy and burial.
Iliana ultimately agrees to marry Galen, to Winnie's excitement and pride, insisting she had never given up on the girl. When the Witch Child mentions two conditions, Winnie is teary with joy and promises Iliana anything she wants, but Iliana claims she does not "want things". When she learns of the second condition, to attend Jaime's birthday party, Keller agrees, but none of the team are happy about the decision. Winnie and Nissa devise a plan to get Iliana to the party and then depart in time for the solstice celebration.
As the team departs for the party, Alex goes to the door. Keller is disturbed when the toddler's face "crumpled" after she had blown him a kiss at Iliana's insistence. Alex begins crying and calls out goodbye repeatedly to Keller, leading Winnie to think Alex might possibly be able to see the future, a sign of his own witch heritage.
At the party, unnerved, Keller warns Winnie to keep alert after she is informed that Alex might be missing. However, this turns out to be a trap; Winnie, along with Nissa, Galen and Iliana, are ambushed and injured outside. Keller finds them and, realizing Jaime is Azhdeha, changes form, managing to slice off three of the dragon's five horns. Winnie regains consciousness and crawls over to Iliana, whispering to her. Iliana recovers and confronts the dragon, summoning orange fire akin to Winnie's; Keller assumes this is what Winnie had been saying to her. However, as Iliana begins chanting the names of other dragons and calling upon Hecate, the panther realizes Winnie could never have taught her such things. Winnie screams for Iliana to fire at the last horn as the Witch Child summons the blue fire, obliterating the dragon, and healing them all.
Winnie, with only some drying blood on the side of her head, calls for the unconscious Keller to awaken; as her boss does, she attempts to drag her and Galen up, as it is almost time for the solstice celebration. The team races to the event, just making it in time, where the crowd applauds them for their work. Winnie reveals that she only tried teaching Iliana how to use the orange witchlight fire, confirming Keller's notion that Winnie never taught her the draconic names or the prayer to Hecate.
At the end of the book, Winnie and the others are brought to a safehouse to relax and recover.
Winnie is given a mention in the short story Thicker than Water; she is among the witches of the hospital ward in Harmony working on healing Keller after her battle with the dragon Whitcombe.
She is also briefly mentioned in the short story Ash and Mary-Lynnette - Those Who Favor Fire, as having "dolled up" Sarah Strange, making her look "frighteningly beautiful".
- The name Winfrith is a variant of the Anglo-Saxon name Winfrid (Winefrith, Winfried), which translates to mean "Friend of Peace". This is fitting considering Winnie's position as a member of Circle Daybreak. The name is shared by the Christian Saint Boniface (born Winfrith), who is considered a patron saint of Germany.
- Winnie bears several physical and personal resemblances to Poppy North - both have curly red hair, green eyes and excitable and happy-go-lucky personalities, and both are compared to pixies or elves in appearance. In addition, both are witches at one point (although Poppy was a lost witch and only discovered this after becoming a made vampire).