Art regains memories of her past as the daughter of a Pirate Queen and she leads her own rag-tag pirate crew onto the high seas to collect treasure, in the process dueling with a rival pirate and falling in love with one of her hostages. Art is a rebellious girl who has been forced to attend the Academy for Young Maidens. One day, as she and the other students are practicing Deportment, Art falls down the stairs and suddenly regains memories of her mother. She remembers that she forgot her mother because a cannon knocked the memories out of her. Art no longer cares about Deportment and behaving like a young lady and everyone thinks she's gone mad.
The Mistresses of the Academy tell her father, who is a wealthy landowner called George. George is furious at Art's misbehavior and Art is furious that her father stuffed her in this prison-like setting when she was destined for great adventures like her mother. Art remembers that her mother, Molly, was a great pirate who called herself Piratica. Her father thinks otherwise, and commands that Art be locked up until she returns to her senses.
Art remembers that her mother stole a merchant trader's ship, called the Unwelcome Stranger. Art also remembers the tragic day her mother died when her ship was overtaken by an enemy pirate who wanted a treasure map. Art was only ten years old, then. Art escapes the Academy and searches for a place called the Coffee Tavern where she remembers members of her mother's crew liked to loiter. On her way to the Coffee Tavern, Art witnesses a Highwayman named Jack Cuckoo rob a coach. Jack is a clumsy highwayman and as he makes his escape, he even drops his pistol right at Art's feet. Art uses the pistol to rob the last passenger on the coach – a young man named Felix who is an artist. She forces him to exchange his cloak and hat for her sooty ones and leaves him inside a warm cottage.
The next day, when Felix enters town wearing the sooty clothing, everyone thinks he is Jack Cuckoo. He flees town and ends up being recruited as a surgeon to oversee a duel between two angry men. Felix again flees, this time with one of the guns from the duel. Felix spends another few miserable days traveling by foot because he's too afraid someone will think he's a highwayman based on how he looks but he's too cold to dump his jacket and hat. When he arrives in “Londun” he is almost caught by the constable but he gets the help of two ice skaters and skates away. The two ice skaters turn out to be Ann and Fan Coffee who are going to visit their Uncle, a coffee merchant. They decide to stop by their Aunt's place and, much to Felix's dismay, he meets one of the men from the duel he fled from. The man also points out that Felix is actually a highwayman. Ann and Fan provide a distraction so that Felix can escape out a window.
Meanwhile, Art, disguised as Felix, hops aboard the Coach and travels to Londun. Art finds the Coffee Tavern and meets the members of her mother's crew. They all seem confused when Art insists that they return to the high seas – they are more interested in selling coffee. Art is disgusted at how these pirates are now living their lives when they used to roam the high seas, finding great treasures. The only ship the pirates have is a small boat decorated to look like a pirate ship which the crew have been ordered by their sponsors to use as they travel down the river, advertising their coffee. Eventually, the crew bring Art to a theater and they finally clarify Art's past. Apparently, Art's mother Molly, was actually an actress that was famous for playing the role of a pirate queen. The crew are really just members of Molly's acting troupe. One of the crew-members gives Art an old map that used to belong to her mother. While thinking about the reality of her situation, Art is accosted by some young men. She grabs one of the swords from the young men and robs them.
One night, Art and her crew are sailing down the river when they see Felix, being chased by constables. Art helps Felix escape. Art uses Jack Cuckoo's gun to fire on the constables and the crew fear they are now all wanted men. Art insists that the crew listen to her as she is the Captain of the ship, now. Most of the crew are too bewildered to protest. She decides that they will continue traveling on the river until they reach the place where their coffee sponsor wants them to do a theatrical show. They will drop Felix off when they arrive in the town of “Port's Mouth”. Art tells Felix that she though she robs people and commits crimes, she will never kill anyone as this is the rule her own mother abides by.
Art learns that the play her mother and the crew starred in was based on real life places and events. In particular, Molly's enemy, Golden Goliath, is based on a real pirate. They take respite at a local tavern that apparently Jack Cuckoo is known to frequent because all the patrons think Felix is Jack and treat him well. Unfortunately, the constable catches up with them and Felix, Art and the crew have to escape again. Art comes up with a plan to steal a trader vessel called the Elephant.
Art and the crew pretend to be drowning so that the sailors of the Elephant save them. When they get aboard the Elephant, they threaten to kill the Captain unless all the sailors get off the ship. The heist works and Art is now in possession of the Elephant. Art tells Felix that she will drop him off at the “Isle of White” while the rest of them continue on a journey to the “Blue Indies”. The crew prove very skillful at navigating the Elephant because they all trained to act out their roles aboard a fake ship so well. Art decides to rename the ship the Unwelcome Stranger. As they sail the ocean, they continue robbing the goods from other trader vessels and selling the goods for a tidy profit at the various ports they pass. Art wants to let Felix off at each port, but at each port, Felix finds some other excuse to remain aboard.
Art and her crew dress up as Republican soldiers and they enter a tavern in “Porto Rex”. There, they meet a beautiful girl who calls herself Little Goldie Girl. Art immediately knows Little Goldie Girl is the daughter of the Golden Goliath. Goldie Girl seems to know that Art is in possession of a certain map and she claims that the map is rightfully hers. Art will only give it to Goldie if she pays a handsome fee for them. At first, Goldie refuses, but Felix uses his charms to convince her. Art ends up giving Goldie a fake map because now she knows that her mother's map might actually be a real pirate's map. Goldie leaves the Unwelcome Stranger but not before trying to convince Art to let her have Felix. Art refuses and Felix is disappointed as he is quite smitten with Goldie Girl.
Goldie Girl finds out Art's map is a fake and chases the Unwelcome Stranger with her own ship, the Enemy. Art and Goldie Girl engage in a sea battle with Art emerging victorious and severely damaging the Enemy by plunking a cannonball through its foremast. The Unwelcome Stranger continues on its journey around the cape of “Africay”. They survive a bout of windless seas followed by a great sea storm before they are captured and brought to a Pirate stronghold. The stronghold is run by a man named Hearst who is a pirate that's somewhat retired. He tells Art he knew of her mother back when she was a pirate. He plans on helping Art to use her mother's map to find the treasure. He shows them two portraits of the Treasured Isles where the treasure is reputed to be hidden.
Art doesn't trust Mr. Hearst so that evening, instead of partaking of his hospitality, she and her crew escape and return to the Unwelcome Stranger. On board the Unwelcome Stranger, Art has a conversation with Felix in which he reveals the circumstances of his upbringing. He explains that when he was but a boy, his father was killed by the Golden Goliath and since then he's hated pirates. He reveals that the only reason he's staying on board with Art is that he plans on keeping a journal of all her acts of robbery and crime so that he can bring all the pirates to justice when he returns to England. This angers and disappoints Art, and she vows to find some way to ruin his plans.
The crew finally discover the Treasured Isle and Art unravels the clues on her mother's map to discover where the treasure is hidden. When they find the chest, it is full of old paper. Upon closer inspection, Art realizes that each piece of paper is actually a treasure map promising to lead to different treasure troves scattered around the world. On their way back with the treasure chest, they are ambushed by Goldie Girl and her crew, who have somehow followed them. Goldie Girl reveals that there was a traitor among Art's crew. Art battles Goldie in a one-on-one sword-fight in which she emerges victorious. Goldie surrenders but is enraged when Art scars her pretty face. After the fight, the crew is ready to leave the island but they are caught in yet another storm. This time, the storm destroys everyone's ships and they are marooned on the Treasured Isle.
Soon after, a group of vessels from the English Republican Navy appear on the horizon and all the pirates think they are doomed to be captured and hung. The Navy treat Art and her crew very well and are even fans of Art's mother so they are allowed to throw makeshift shows on deck to entertain the Navy Captain. Felix is the only person out of the crew that is not imprisoned because he told the Navy Captain that he was Art's hostage. When the Navy returns to England, all the crew-members are sentenced to death. But Art is a celebrity among the peasants, who regard her as a hero. Goldie Girl, however, manages to charm the judge by pretending to have been kidnapped by her own father against her will and forced to become a pirate. She is pardoned while the rest of her crew are sent to the gallows.
Meanwhile, Art tells her crew to escape out of the chimney of the guard house while they are having their last dinner before hanging. She is not due to be hanged until three days after her crew so she thinks she will have time to figure out a way to escape. Her crew succeed in escaping and all of England spread the tale of their cleverness. On the day of her hanging, her crew have a plan to try to help her escape. The crew try to save Art but the constable's men are everywhere. Suddenly, Felix makes his appearance on the scene and commands the audience's attention by talking about how Art may be a pirate but she doesn't kill people. He ends his rousing speech by asking the people to stand up for Art, who is their hero, or else kill him as well. The people are moved and they rise up against the constable and his men to allow Art and Felix to escape.
The story ends with Art and Felix kissing and planning on going on more pirate adventures together.
Best part of story, including ending:
I really love Tanith Lee's creativity as she always seems to pen humorous and absurd stories where the readers are deeply engaged and sympathetic towards her characters and the plot. I specifically like how Art thought she was a normal girl but then discovers she was actually the daughter of an actress, and then finally figures out that she's the daughter of a pirate. I also like that Piratica is a story about female pirates and Art and Goldie Girl fighting over Felix was hilarious.
Best scene in story:
I thought it was funny how poor Felix got more and more involved in the story simply because he donned Art's sooty jacket. My favorite scene was when Art first meets Felix while she is robbing him of his clothes. I thought it was funny that on the one hand, she was robbing the poor fellow, but on the other hand, she made sure Felix doesn't freeze to death.
Opinion about the main character:
I like that Art was spunky and honorable in a world where dishonorable behavior is the easier solution to most problems. I like that Art was clever and always hankering for an adventure as it made the plot move forward very quickly and in an entertaining way.