|“||We save each other. That's how it works.||”|
In fandom, this relationship is sometimes known as Dalek.
Deryn and Alek first meet when Alek revives Deryn after the Leviathan crashes. Alek believes that Deryn is a boy because she introduces herself as "Dylan." Though he brings medicine and supplies, Deryn is suspicious of him and calls for him to be captured. Alek threatens her with a pistol, but Alek relinquishes the gun when the sniffer dogs scare him. However, after this rocky start to their relationship, they slowly grow to trust and respect each other and form a friendship.
Eventually, Deryn develops a crush on him after he tells her his real identity and the story of his parents' deaths and his flight from Austria-Hungary, but Alek is unaware of her feelings. Deryn describes Alek as "handsome", and feels an "odd kind of tingling" when he hugs her. She insists that she is not a "girl twisting her skirts" when she thinks about him. However, their relationship is complicated by the fact that they are still on opposite sides of the war, and that Alek believes her to be a boy and does not know that she has romantic feelings for him.
When the captain asks Deryn if she knows anything about Alek, such as his identity, she lies and says that she doesn't know but will tell him if she finds out anything. When she tells Alek about the captain's order, he tells her that she must tell the captain about him because she would be committing treason by disobeying an order. She almost tells him that she will not be hanged because she is a girl, but is interrupted by Dr. Barlow.
Deryn has fallen in love with Alek as their friendship grows, and she struggles to keep her emotions at bay and well hidden. She has been teaching Alek how to climb ratlines, and Alek has been teaching her to fence. A part of her wishes that she could reveal herself to him as a girl in the hope that he might return her feelings, but she is also afraid that he will reject her considering she is a Darwinist and a commoner. Fearing that their friendship might be at risk, she keeps her feelings to herself. Before Alek's escape from the Leviathan, he confesses he has fallen in love. At first Deryn had thinks that he means her, almost believing he has discovered her secret, but Alek continues his confession that he has fallen in love with the airship. However, it is fairly apparent throughout the series that Alek has a subconscious obsession with "Dylan" and how much he admires "him".
Later, Alek and Deryn reunite in Istanbul, and Deryn discovers that Alek has joined forces with the Committee for Union and Progress. Deryn immediately takes a dislike to the committee leader's daughter Lilit, fearing that she and Alek are becoming close. She continues to dislike Lilit until Alek tells her that Lilit is more interested in "Dylan" than in himself.
Deryn is willing to risk almost everything for Alek. She even goes to great lengths to find him in Istanbul and to help the Committee. Alek possibly sees Dylan as his strongest ally, admitting he can't end the war without him by his side and begs him to come along with him into hiding. Deryn refuses to go but instead pleads and convinces him to go back with her to the Leviathan. However, she does wish that Alek would say that he wants her to come with him because he loves her, not because she would be useful to him.
Alek and "Dylan's" relationship has grown into a strong trusting friendship. They help each out by sharing rather personal and precariously situated secrets (save Deryn's real gender), and spying on others for information in order to try and help each other out. Deryn even looks the other way when Alek and his men escape from the Leviathan.
Alek confesses to Deryn that he wished he could be, or would've been just like her if he wasn't born into royalty. From forming plans to fights on the battlefield, the two of them find themselves becoming an a unstoppable team. And though at times they do disagree, they still trust each other enough to go through with anything.Eddie Malone. Although he has trouble believing it, Alek tests this possibility by tricking Deryn into responding to her real name. Deryn punches Alek when he accuses her of not being a real soldier. Because the truth did not come from Deryn herself, Alek distances himself from her. He feels ashamed of not noticing and betrayed since he had told her all of his secrets while she did not. After a few days, Alek talks to Deryn and they return to their relationship as friends, as both of them were depressed without the other, and they do not want to make anyone suspicious.
While trying to attach a radio wire to the top of the airship, the two are stuck on Leviathan's topside during a hurricane. After knocking his head, Alek states that only now does he truly sees Dylan as Deryn. Because of his head injury, Deryn insists that they have to keep talking in order to keep Alek conscious. During their conversation, Alek insists that Deryn promise him that neither of them will ever lie to the other, or keep secrets from the other. Alek also promises to help Deryn keep her secret at any cost. True to her promise, Deryn kisses Alek to show her true feelings, but also to keep him from passing out. She tells him that she knows that because she is a commoner and he's a prince, there can be nothing more. However, Alek still remembers their kiss much later, though he tries to dismiss it after a conversation with Volger.
After Deryn is injured, Deryn and Alek tell the truth to Dr. Azuela and Pancho Villa so that Deryn can recieve proper medical treatment. Unfortunately, Eddie Malone overhears the truth about Deryn. Feeling that it is inevitable for the reporter to reveal the secret, Alek helps Deryn to enjoy what they suppose are her last days aboard Leviathan. Alek changes his mind about letting things go as it is and offers Malone a bigger scoop about himself to keep his promise to Deryn, and allows Malone to write about Alek being the rightful heir to the throne of Austria-Hungary. But in doing so, Alek and Deryn must go their separate ways, as Deryn is now able to stay on the airship and Alek feels that he must stay in America to support Tesla.When Alek learns that Tesla wants to stop the war at all costs, killing anyone who gets in his way, including Deryn, Alek realizes that he must bring Goliath down. When the struggle against Tesla and Goliath is over, Alek realizes that while trying to stop Tesla and eventually killing him, it had not been the millions of lives or the Leviathan itself that Alek wanted to save the most, but Deryn alone. When Alek tells her this a few weeks later, Deryn tells him that he shouldn't tell anyone else or he could be accused of supporting the Darwinists in the war.
And as they stand together on the topside, Alek confesses his love to Deryn with a kiss. He throws away the letter from the pope and says that the letter represented his past, which he had clung to needlessly. But now that he has Deryn, he has a reason to go on without his parents and his past. When Deryn asks him what he plans to do without his letter, Alek says he needed a proper job, and Deryn asks him to consider working with her alongside Dr. Barlow. In a later newspaper article, Eddie Malone reports that Alek accepted a job offer from Dr. Barlow, and that Alek's only comment was the Hapsburg motto, Bella gerant alii, tu felix Austria, nube, which implies that Alek plans to marry Deryn.