A timeline of events:

September, 1689
Robert Martinson, a ship captain, loses his ship and crew to a powerful storm off the coast of Ireland. He eventually washes up on a beach raving and drooling about “Sea Serpents.” Two-weeks later, after recovering, he begins to create a strange religious following preaching about the worship of these creatures among superstitious fisher-folk.

June 14, 1692
Roger Martinson and his followers flee religious persecution and settle in Monhegan Island, off the coast of Maine.

1692-1777
Every year the islanders, led by Martinson and eventually his descendants, conduct a sacrificial ceremony on the beach of Monhegan Island in which one or multiple islanders are “given up” to the creatures from deep below. The islanders discover their reward in bountiful harvests from the sea the following season.

A day after the ceremony the Martinson family will find trinkets and treasure, presumably from ships long-lost to sea, graciously dumped in the cellar of their house. This cellar coincidentally has a trap door and tunnel that leads directly to the ocean.

1778
Richard Martinson (Robert’s grandson) grows concerned by the declining population on the island. As it turns out, small communities of inbreeding tend to suffer health issues. Richard decides that all future sacrifices will be “outsiders” (mainlanders). From that year on, the islanders begin luring unsuspecting victims, often loners and outcasts, to the island to act as sacrifices.

May 5, 1894
Alan Martinson dies suddenly at the age of 48. He does not pass the secret of the ceremony to his son, Roger. The ceremony is forgotten, and the book describing its details remains hidden in an attached bedroom in the Martinson house.

1921
The catch for Monhegan Island’s fishermen drops off dramatically. Concern grows amongst the inhabitants of the island.

1922
The catch is even worse than the year before. The people on the island pressure Roger Martinson, the youngest and last descendant of the Martinson family, to resume the ceremony. Martinson agrees, re-discovers the book, and begins preparations.

June 14, 1923
The ceremony is successful. Angela Blackwood takes the role of “sea nymph” and is found after to have lost all sense of self. This does not particularly bother Roger Martinson.

June 14, 1924
The ceremony is once more successful, with Brandy Collier acting as sea nymph this time. The islanders are happy; the catch of fish the previous season increased dramatically.

June 1, 1925
No suitable outsiders have been found for this year’s ceremony. In desperation, Martinson puts a plan in action, faking Sara Goodwin’s death. In reality, she is hiding in the woods of the island per his instructions.

June 3, 1925
Detective Sam Poole, cousin of Lt. Martin Poole (now of Boston PD), arrives to conduct the investigation, but is forced to conclude she “drowned” due to lack of evidence and uncooperative islanders… despite his many suspicions and misgivings.

June 12, 1925

Martinson contacts Jonah Kensington to have some private investigators look into Sara’s “disappearance” as the police were unable to help. His true intention is to find a few people that will not invite too many questions when they are mysteriously “lost at sea.”

June 13, 1925
The investigators bang around Bangor, looking into potential leads. It is clear that the mainlanders hold no love for the islanders, to the point where a young woman’s disappearance on the island does not make the local news. The whale vet discovers she has somewhat of an unnatural affinity for the ocean.

June 14, 1925
The investigators arrive on the island. Roger greets them warmly. Despite his affable nature, the investigators do not seem to fully trust him. This may be because he has two seemingly brain-dead women following him around. He invites them to explore the house and the island, asking only that they respect his privacy and locked doors. Surprisingly, the investigators are polite and do adhere to this, although Anastasia does insult their host by insinuating he’s a pedophile.

Exploring the village at the docks, they find most of the islanders unhelpful and malevolent in disposition. Only the owner of the pub and his waitress will speak to them, and the owner cuts the conversation off quickly when he overhears his waitress make reference to a “ceremony” that night. She is clearly nervous. Gertrude hides under a table overhearing this, before subtly escaping back into the street.

The investigators return to the house for dinner. Chaz switches plates with Anastasia, knowing revenge for her earlier insult likely occurred. Martinson retires to bed after smoking some cubans, while the investigators discuss their day.

Martinson heads downstairs later that night. He is not particularly quiet. In fact, he is almost intentionally loud enough for the investigators to hear him, allowing them to follow him out the house and through the woods of the island to the beach where the ceremony will take place. The investigators spread out and hide in the woods, watching as multiple islanders and the “missing” girl Sara show up. There is a general feeling of excitement from the group of islanders.

Sara drinks a concoction and then heads into the water, conducting some horrible chant in a dead and evil language. At the same time, Brenda and Leonard are captured by islanders – Roger knew the investigators would follow them to the beach. Brenda and Leonard are tied to a peculiar stone slab on the beach just in time to witness six giant reptilian fish/frog hybrid “creatures” emerge from the water toward them. The islanders, their work done and not particularly feeling the need to remain, flee quickly.

Strangely, Brenda is not surprised to see the creatures, and does not feel particularly threatened by them, although she’s not sure why.

Anastasia, totally-not-a-spy instincts kicking in, decides to try the chant she recently learned in the book from Corbitt’s house. Successfully saying the dark words, her gun melts and then reforms into a towering, dark, planar “Shambler” of death. Despite this being intended, this snaps Anastasia’s mind temporarily, and a lust for murder overtakes her.

Chaz, unsure of what to do, runs over to help Anastasia, attempting to spray her with holy water. This is not particularly effective, and the Shambler protects its summoner by sinking its night claws into Chaz’s shoulder-blades.

On the beach Leonard manages to free himself from his bindings with his knife, but rather than run himself, stays to help free Brenda. As soon as the bindings around her feet are cut, Brenda bolts to the woods, leaving Leonard behind.

Leonard is abducted by the water creatures, who take him back into the ocean. His friends, otherwise occupied, last see him thrashing against their hold as they forever submerge him into the depths of the ocean.

Chaz attempts to shoot the Shambler, but is unable to get a shot off with the claws muscle deep in his shoulders. The Shambler folds space and both Chaz and it leave this quantum universe behind.

Gertrude runs and tackles Anastasia as all this is happening, hoping to stop Anastasia from accidentally killing a friend with her remaining gun. This angers Anastasia further, and in her blood rage attempts to shoot the 16 year old girl detective. Due to the force of Gertrude’s tackle (she is a homely girl afterall), Anastasia’s arm swings wildly while shooting, and her own bullet pierces her thigh. The shock of pain pulls her out of her stupor, where she wakes to find two friends missing and a bullet in her leg.

Feeling an urgent need to cut their losses, they flee through the now deathly quiet island to the wharf, where they find Martinson’s body-man, Alen Krebs, loading their things on the boat. It appears his orders were to crash the boat and dump their belongings out at sea, faking their deaths plausibly. Under threat of impalement from Brenda’s harpoon gun, he instead takes the three remaining women back to the mainland.

June 15, 1925
While Anastasia receives medical treatment, Gertrude and Brenda return to Sam Poole to report the evils of the island. Unfortunately he is unable to corroborate their story, as Martinson denies ever having met the investigators (the investigators also failed to notify Poole who had originally hired them to investigate Sara’s disappearance), and nobody on the island will confirm they were even there.

June 18, 1925
A headless body washes up on the shores of Maine. The police are unable to identify the victim. This is likely because Alan Kreb’s head is buried deep underground on the island.