Requiem

"" is the ninth episode of the first season of Sanctuary, and the ninth episode overall in the series.

Synopsis
Dr. Magnus and Will investigate a distressing call for help deep from the merfolk below the Bermuda Triangle, resulting in a deadly battle to save Magnus' life.

Cold Open
Inside a submarine, Dr. Helen Magnus, wet and confused, watches the read-outs on a screen. She hears a noise and looks at the air vent as it closes. Hurrying around the small room, checking the air vents, she realizes that they are all closed. She eventually goes back to the monitor, seeing the CO2 and oxygen levels change.

She rushes back to the door and looks through the glass porthole at Dr. Will Zimmerman, who looks back at her with a determined look on his face. Magnus begins to gasp for air, falls to the floor and takes a last breath as Will watches.

Act I
The Sanctuary submarine Nautilus is in the Milwaukee Deep, off the coast of Puerto Rico. Magnus and Will are the only ones on board, discussing a number of the significant historical figures the Head of the Sanctuary Network has met during her long life. They get a call from Henry Foss, who informs them that Sally the mermaid, who asked them to investigate a telepathic call for aid from her people, has had no further contact with the Merfolk. Henry also points out how exciting it must be for them, since they are currently in the actual Bermuda Triangle. Magnus rebuffs their speculations, as there is nothing spectacular about the Triangle except that a higher than average amount of abnormal see life resides here.

Will eventually finds the merfolk: there has been a massacre among their kind, and now over a hundred dead bodies float in the deep, a catastrophe for a species as rare as the merfolk. Magnus and Will bring a female specimen aboard and realize that she was not killed by an animal. Magnus finds a clear fluid that she cannot identified, and opts to return to the surface. Soon afterwards, she notices a headache and strange spasms in her hand.

Will is reading a book when suddenly he hears a loud noise; Magnus has collapsed and her head hurts more and more. She tells him that something is wrong.

Act II
Magnus feels an intense pressure and bleeds from the nose. She wants to stop the Nautilus from returning to the surface in order to find out what is going on. They soon return to their original depth. Magnus gets better again, while Will has no symptoms of any kind.

During an analysis of her blood, Will asks Magnus some questions about how Ashley is coping with the fact that her father is Jack the Ripper. Magnus rebuffs him and wants to leave, and they have an argument. He tells her that she and the team are the first people he ever really connected to, while she explains that after all the friends, colleagues and lovers she buried, she is reluctant to get to close to people. However, she feels that he is doing great and that he could replace her in case something happened to her. Just then, Magnus has another attack and they have to go deeper again.

The blood analysis gives them no clues. Will suggests looking for a parasite, and Magnus scans her body for unidentified elements. The computer soon discovers a microscopic parasite in her brainstem that is multiplying and taking over her brain.

Act III
An autopsy of the dead mermaid shows that she too was affected by the parasite, which all but destroyed the logic center of her brain: the Merfolk tore each other apart after getting infected. When Magnus checked the body, the parasite penetrated her gloves and moved to her body, which is now showing more and more symptoms. There seem only two choices: if they return to the surface, she will die, and if they stay, she will eventually turn into a raging killer.

Magnus injects herself with a compound that should make her body a less good host for the parasite, but her body immediately reacts by attacking Will and ordering him to take them deeper.

Later Magnus apologizes and tells Will she would never have infected him deliberately. He is concerned about her seeming to loose control of her emotions. They continue to go deeper, but the Nautilus has limits where depth is concerned. Magnus tells Will that in the event that she is no longer in control of herself, he must act decisively.

Magnus still feels pain from the pressure, and takes the sub deeper. At 2,400 feet, the hull of the Nautilus begins to show signs of weakness.

Act IV
As water begins to enter the hull, Magnus becomes more and more aggressive. At almost 3,000 feet, the ship hits an underwater mountain shelf, and stops. The engine room and the primary cargo hold are flooded. When showing Will where they are on a monitor, Magnus knocks him out from behind.

Will wakes up and realizes he is cuffed to a chair. Magnus accuses him of lying to her and trying to profile her like a criminal, telling him that while he wants to save her, it was actually she who saved him from a life of mediocrity and shame, and that she can save him again. He realizes that she herself made them lose control of the sub. He tells her that he agrees with her that they must go deeper, but that they must go somewhere else for that.

Magnus then enters the flooded section of the ship, while Will uses the time alone to free himself. He tries to lock her in the flooded section, but she returns and takes him with her in order to help her use a control panel. After they are successful, she takes off his oxygen mask. He returns to the section that still has air and points a gun at Magnus, who follows close behind. Unimpressed, she just tells him not to miss.

Act V
Magnus confronts Will and takes the gun when he refuses to shoot. In her rage, she tells him that no one lives forever, and pulls the trigger. However, Will has removed the magazine. She leaves him behind to take the ship deeper, but gets locked in the control room by Will, who removes the oxygen from that section (at this point, the plot returns to the opening scene). Magnus soon looses consciousness and a clear fluid leaves her body: the parasite is looking for a new host. Will freezes it and revives Magnus, who soon returns to her former self.

Some time later, the Nautilus is secured and Magnus and Will have a talk. While Will states that Magnus may have lived for a long time, but that her work is not yet done, Magnus explains that her work will never be done, and that the day will come when he will have to take over. Yet, they both agree that that day is not today.

Extras

 * This episode has a DVD commentary track. Commentators: Damian Kindler, Amanda Tapping, and Martin Wood.