Wren is described as having coppery hair, grey "mariner" eyes, and a long "beaky" nose. Prior to the start of A Darkling Plain she has her hair cut into a lopsided bob that causes Theo Ngoni to think she is standing on a slope in a photo.
Wren has her father's naivety at times but she is also intelligent and kind. She also has her mother's determination and can be quite willful at times.
Wren is fifteen and eager for excitement away from sleepy Anchorage-in-Vineland. Then, the Lost Boys turn up looking for the Tin Book of Anchorage and she agrees to help them find it if they take her with them back to the outside world. However, the Lost Boys trick and steal the Tin Book off her. Wren is take aboard captive; Hester tries to save her, and starts shooting the Lost Boys. However one survives, a boy named Fishcake, who takes her back to Grimsby, the Lost Boys base with the Tin Book.
However, before Wren and Fishcake get to Grimsby, they come across Brighton, a Traction City of which Nimrod Pennyroyal is mayor. Brighton captures their limpet (submarine) and Wren is sold as a slave to Pennyroyal by Nabisco Skhin, a slave dealer and head of the Skhin Corporation. Wren spends the next few weeks of her captivity plotting to escape. She approaches a fellow slave, Theo Ngoni, an aviator who used to fly Green Storm tumblers. However he refuses, so Wren tries to steal Pennyroyal's air-yacht and fly back to Anchorage. Her plan goes wrong and she is caught, but helped out by the Mayoress and escapes punishment. Meanwhile, her father, Tom, is captured by the Skhin Corporation and Wren is forced to steal back the Tin Book from Pennyroyal, who kept it after Wren was caught, for Skhin.
Wren asks Theo Ngoni for help and he agrees. Together, they steal the Tin Book from Pennyroyal's safe. However, the Green Storm and Stalker Fang are also looking for the Tin Book and attack Brighton the same night Wren steals it. Wren and Theo are captured by the Green Storm who take the Tin Book from them. While the Stalker Fang is reading the Book, Oenone Zero, the Stalker Fang's surgeon-mechanic, lets them escape. They flee from the Storm and come across Pennyroyal who is injured. The three of them hide until Tom and Hester find them from the Jenny Haniver, their old airship which Pennyroyal took in Predator's Gold. However, Wren has learned from Pennyroyal about how Hester betrayed Anchorage to the Huntsmen of Arkangel, a secret Tom does not know about. Hester is about to kill Pennyroyal until Wren blurts out her secret. Tom confronts Hester, who flees into the desert, in despair. Tom suffers a heart attack but Wren and Theo help him and Pennyroyal onto the Jenny Haniver and fly off.
Wren and her father have been traveling and trading in their airship the Jenny Haniver for around six months. They are on the Traction City of Peripatetiapolis when Tom spots a woman who he believes is his old Guildmate from London, Clytie Potts. The woman, however, gives her name as Cruwys Morchard and denies knowing Tom. Tom is unsatisfied and Wren suggests that they try and find out more about her. They track Nimrod Pennyroyal, from whom Tom once heard the name, to Murnau, a city part of the Traktionstadtsgesellschaft. They don't get anything useful out of Pennyroyal, but they do meet Wolf Kobold, the son of the Kreigmarshal of Murnau. Wolf, like Tom, also thinks that there may be survivors of MEDUSA living in the wreck of London, having had a mysterious experience there when he went to the city a few years earlier. The trio agree to investigate and begin preparations.
Tom and Wren move the Jenny Haniver to Wolf's suburb, Harrowbarrow, and begin traveling towards London. At the Green Storm's front line, Harrowbarrow is used to create a diversion and the three of them go forward in the Jenny unnoticed. They reach the wreck of London and soon after they land, they are captured by a group of young Londoners. Their leader, a man called Garamond, leads them to Crouch End, a place in London serving as their headquarters. There they meet Cruwys Morchard, who is actually Clytie Potts, and Chudleigh Pomeroy, the former head of Tom's Guild, who is now the Lord Mayor of London. Though the Londoners welcome them seemingly wholeheartedly, they are forbidden to leave, making Wren suspicious. After some snooping around, Wren and Wolf stumble on to New London, a town which the Londoners are building, powered by magnetic levitation. They are caught spying by the paranoid, head of security, Garamond. The Lord Mayor, however, thinks them trustworthy and introduces all of them to New London. Wolf soon escapes though, and plans to return to London with Harrowbarrow to devour their new city.
A few weeks later, Wren is on a patrol with some of the other young Londoners. The spot an intruder, pursue him and realise it is actually Theo Ngoni. They take him back to Crouch End but at the same time, a flock of Green Storm Raptors (resurrected birds) attack them. Theo grabs a lightning gun and manages to shoot down several of the birds. The other Londoners are puzzled by the newcomer but welcome him into the community. However, Garamond, the head of security, is very suspicious of Theo, as he is an Anti-Tractionist from Zagwa. Later, Wren shows New London to Theo, who is doubtful about it. However, ODIN, controlled by the Stalker Fang, strikes several cities of the Traktionstadtsgesellschaft, lighting up the whole Hunting Ground. The devastation is seen from London and that night, Tom leaves for Batmunkh Gompa in the Jenny Haniver, in an attempt to persuade General Naga (who Tom believes controls ODIN) to not use it on New London. Theo and Wren are left alone in London. However, the night Tom leaves, Chudleigh Pomeroy, the Lord Mayor, dies in his sleep. The paranoid Garamond is appointed as the new Lord Mayor and has Wren and Theo arrested. He then proposes that Theo be killed, believing that he is an agent of the Green Storm. Theo and Wren are locked up but Lavinia Childermass, the leading scientist working on New London, thinks they are innocent and sets them free. They escape through the debris fields.
Leaving the debris fields of London, Wren and Theo encounter Harrowbarrow approaching. Theo runs back to warn the Londoners, as Wren boards Harrowbarrow and tries to and convinces Wolf to lead Harrowbarow down "Electric Lane", a clearing where anything metal is struck "sprites", powerful blasts of lightning left over from MEDUSA. At the same time though, Naga and a Green Storm fleet arrive in London, as they believe that ODIN is being controlled from there. The Londoners demonstrate New London's levitation ability to Naga who decides to help them defend it from being eaten Harrowbarrow. Wren's plan succeeds and Harrowbarrow is struck by a sprite. However, it is not enough to destroy the suburb completely and it is soon moving again. Wren, knowing that Wolf Kobold realises she has betrayed him, narrowly escapes from the suburb. While escaping she comes across Theo who has been looking for her. They are looking for a way off Harrowbarrow when Wolf confronts them in a duel. Theo fights bravely against him but he is easily outclassed. However, a rocket from a Green Storm airship hits the suburb: Wolf falls and dies;Wren and Theo are rescued by Naga. Harrowbarrow still chases New London, who has started moving out the debris fields, but Naga sacrifices himself in a kamikaze attack, finally stopping Harrowbarrow. New London escapes.
The last that is heard of Wren is when she is writing a letter to her friend Angie in New London from Theo's house in Zagwa. It mentions their engagement and that they have bought an airship called the Jenny Haniver 2 and plan to set up as air traders of magnetic levitation furniture. Theo also got a letter back from Oenone Zero, now Widow Naga, explaining what happened after Theo left: Hester and Shrike rescued Tom the night they landed in Batmunkh Gompa and flew to Erdene Tezh. They are believed to be dead though, as the burnt out wreck of the Jenny Haniver were found in the valley of Erdene Tezh.
Wren is dead by the epilogue, and it is possible that the children Shrike later tells a story to are the distant relatives of Wren.
Tom Natsworthy is Wren's father.
Hester Shaw is Wren's mother. They have a strained relationship.
Theo Ngoni is Wren's fiance.
Katherine is Wren's late aunt. Wren has been compared to her in appearance and personality in Infernal Devices and A Darkling Plain.
Tildy Smew is Wren's best friend.
Angie Peabody is a friend of Wren who lives in New London.
- Wren's resemblance to Katherine Valentine in personality and appearance is often noted in books three and four.