Sun, 8 May 2011
The TARDIS crew, following a distress call, lands aboard a 17th-century pirate ship stranded in the middle of the ocean due to the lack of wind. Its captain, Captain Henry Avery, and what is left of its crew fear a seductive siren-like creature that marks those injured with a black spot on the palm of their hands, then appears and apparently destroys them. In a tussle with the crew, Rory receives a cut on his hand, and also receives a similar black mark. The Doctor orders everyone inside the ship, believing them to be safe away from open water, but the siren appears through seeped water and takes another crew member. The Doctor, Amy, Rory, Captain Avery and the remaining crew secure themselves in the ship's dry magazine. There, they discover Captain Avery's son, Toby, who had stowed away aboard the ship, unaware of his father's illicit deeds. Though uninjured, Toby has come down with a fever, and shares a similar black mark on his palm.
The Doctor and Captain Avery, after a brief conflict over who is in charge, leave the others to try to bring the TARDIS to them. They make it inside safely, but the Doctor finds the TARDIS is acting haphazardly and they are forced to evacuate it before it dematerializes to an unknown location. As they return to the others, the Doctor realizes that the siren is using reflections to appear to them, such as that created by still water. They race back to warn the others, and destroy any reflective surface on the ship.
A storm begins, and Captain Avery has Amy, Rory, and the Doctor help him to hoist the sails to allow them to leave. In the chaos, Toby, while trying to bring his father his coat, drops a polished crown from it. The siren emerges from it and appears to disintegrate Toby. Soon, Rory falls into the ocean, and the Doctor rationalises that the siren has shown intelligence and will likely get to Rory before he drowns. The Doctor convinces Amy and Captain Avery to prick themselves to allow the siren to take them as well so they can negotiate with it.
They soon find themselves aboard an alien spaceship, its crew long dead from exposure to an Earth virus. The Doctor surmises the spaceship, the source of the distress signal, is trapped at the same time-space coordinates as Captain Avery's ship. Furthermore, the siren uses mirror-like portals to travel between the two ships. Further exploration reveals a bay where all of Avery's men, including Toby and Rory, are in medical care, along with the TARDIS; they were taken by the siren, the black spot being a tissue sample for reference. When they try to rescue them, the siren appears and turns violent on them. The Doctor realises the siren is a medical program, seeking to heal the injured crew. The Doctor and Amy convince the siren to turn Rory over to their care, while Avery decides to stay with his son and his crew in the ship, unable to go back to England himself while the ship will care for his crew. Using Rory's nursing knowledge, Amy and the Doctor are able to revive Rory after he is removed from life support. The Doctor teaches Captain Avery enough of the spaceship's controls to allow him, Toby, and his crew to explore the stars.
In the epilogue, the Doctor and Amy talk about mutual trust; Amy confides to Rory that they still cannot talk to the Doctor about his future death, while the Doctor secretly finds his pregnancy scan on Amy remains unresolved.
"Eye Patch Lady" (Frances Barber) appears for the second time in this episode. Similar to her first appearance in Day of the Moon, she appears to be looking through the other side of a small sliding window in a door despite the fact that the window is actually in the solid timbers of the ship and disappears when it is closed.
 Writing and casting
The episode was written by Stephen Thompson. The producers wished to develop a Doctor Who episode set on "the high seas." The episode was also made to allow the Doctor and his companions to "kick back and have some fun." As the episode was pirate-themed, the producers wanted to fit in as many elements from pirate fiction into it, including treasure, mutinies, a stowaway boy, walking the plank, storms, swords and pirates with a "good heart" and "not really evil." However, Arthur Darvill noticed that a parrot was not included. "The Curse of the Black Spot" was originally planned to be ninth in the series but the order was changed during the production process.
Hugh Bonneville plays Captain Avery. Matt Smith and Karen Gillan described Bonneville as "great fun." Bonneville previously played Sir Sidney Herbert and Tzar Nicholas the 1st in the Seventh Doctor audio drama The Angel of Scutari. Lily Cole was cast as the Sea Siren. The producers were looking for an actress who is "beautiful," "striking," and yet somewhat "spooky." Cole came early into suggestions, and she accepted the role.
 Filming and effects
Filming took place primarily in Cornwall and the Upper Boat Studios in Wales. The exterior of the pirate ship was filmed at a dock in Cornwall, while the lower decks were built from a set at the studio. The principal challenge to film at the dock was to ensure the audience would not see it. The crew set up smoke machines to simulate fog. To create the storm the crew used wind and rain machines, the latter of which went through 15,000 litres. The loud noise from the wind machines caused communication difficulties during takes. Anticipating they would get soaked, the cast present on the deck wore dry suits underneath their clothes. Before filming the storm sequences began, Darvill heard that he would perform the stunt where he is thrown into the sea, and was willing to perform it. However, the stunt would later be performed by a double.
The scenes in which Cole appeared on the ship was done by using a harness as if she was flying. Because the actress wore green dress and makeup, the conventional greenscreen was replaced by bluescreens in the studio. Cole felt it was fun to fly on the harness, but found it painful after a few hours. Gillan was allowed to perform several of her own stunts in the episode. She was excited to learn that her character would fight pirates with swords, and was taught how to handle one with basic moves. Gillan was also allowed to swing across the ship. However, a stunt double was required to film the sequence where Amy is thrown across the deck by the Siren.