[2] Infant Isla turns up one day in a shipwrecked boat, and is adopted and raised by the town's mayor Bobby Bentham (Clayne Crawford) and his wife Grace (Lara Jean Chorostecki), whose pregnancy ended in miscarriage shortly before Isla's discovery.
It is soon discovered that Isla has healing powers to cure any ailment suffered by those who are near her, including the dementia of Grace's mother Faye (Frances Fisher).
It is revealed that the island has been inhabited for generations by the same families, and since Isla's arrival they have shut themselves off from the outside world, becoming a Neo-Luddite colony.
The next day a group of children, including Junior, play a game they have often done in the past where one of the them eats poisonous berries and runs to Isla's house to be healed by her before suffering from the effects.
Beau attempts to treat Phillip by pumping his stomach and performing chest compressions when he stops breathing but the child dies just as Bobby and Isla enter.
They call a town meeting to discuss Isla's lack of powers and instruct Beau to re-open his clinic.
One night, it is revealed that the villagers regularly hold a support group, led by Faye, who is becoming the de facto leader of the island, despite her dementia slowly returning.
Faye later approaches Bobby, giving him her stash of Temazepam from before they closed off the island, to drug Isla so that they can take her out on the water and fish, in order to survive the coming winter.
A police officer introduces herself and Social Services agent, Emily, and explain that after Frank and Nancy reached the mainland they expressed concerns about Isla and they have come to check about her welfare.
Emily goes into the house to speak with Isla while outside, tensions rise as the police officer notices Dillon becoming confrontational and asks him to back off.
She walks slowly back to the cliffside she used to go to with Junior and watches as multiple police boats arrive at the island.
[4] Jared Mobarak of The Film Stage wrote that "with potent performances and a gorgeous, textured aesthetic, The King Tide proves a mesmerizing experience above and below its surface.
The terror here isn’t in just how powerful Isla is, but in what an infected groupthink that loses its grip on decency is willing to do in her name to unwittingly push her into discovering the full breadth of those abilities.
"[5] Sheri Linden of The Hollywood Reporter wrote that "whether the characters are forthright or devious, all the performances are in sync with the rugged seclusion of the setting, as is the rustic-meets-old-timey aesthetic of the production design (by Adriana Bogaard) and costumes (Charlotte Reid).
Against the wild natural beauty, calls for “solidarity” are coded warnings against dissent, and promises of “a safe place” are, as Beau drunkenly and accurately declares, a load of crap.
"[6] The film employs many literary devices and themes such as magical realism, lost paradise and Neo-Luddism, the rejection of technology and globalization.