Locke and Key season two finally landed on Netflix last week and took the story to exciting new heights, as Tyler, Kinsey and Bode found themselves defending against more vicious attacks from the malevolent Dodge.
Making matters particularly difficult is that their cunning nemesis is not a mere mortal, but an "Echo" of someone their father once knew, meaning they cannot be defeated by conventional means.
Following the latest batch of episodes, which arrived more than 18 months after the show's initial debut, some viewers have been left scratching their heads over the exact nature of an Echo and how they differ to a human.
Fortunately, we have the answers, so read on for Locke and Key's Echo explained.
Locke and Key's Echo explained
While an Echo has proven to be a terrifying problem for the Locke children to contend with, they are not inherently evil and have in fact been allies to the family at certain points in the comic books.
The Echo is created when someone uses the Echo Key to enter the Wellhouse on the grounds of Locke Manor, and then calls the name of a deceased person they wish to speak to.
In the source material by Joe Hill, members of the Locke family have used this to communicate with lost relatives, getting advice or closure on emotional challenges in their life.
This was what gym teacher Ellie Whedon had intended when she summoned the Echo of her former lover Lucas Caravaggio, who was killed under grim circumstances when he was possessed by a demon from beyond the Black Door.
Unfortunately, she did not anticipate that the same demon that took hold of his soul would return with him in Echo form, making this twisted new Lucas a grave threat to the people of Matheson.
This unpleasant surprise confirms that the Wellhouse brings back an Echo of the chosen person's soul in the state it was in at the time of their death – which is why the newly resurrected Frederick Gideon is such a threat.
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Who plays Echo in Locke and Key?
Dodge takes several forms in Locke and Key and has therefore been played by three members of the Locke and Key cast, with Laysla De Oliveira, Felix Mallard and Griffin Gluck sharing the role in the first two seasons.
Locke and Key: Differences between an Echo and a human
The crucial difference between an Echo and a human being is that Echos cannot be killed by physical means, allowing them to survive perilous situations and even the most brutal of fights.
As a result, the Locke family must find a way to defeat their nemesis using the magical powers that the keys grant, with one option explored in the new season being confining Dodge to the Wellhouse.
Indeed, another important thing that separates an Echo from a human is that they cannot step in or out of the Wellhouse without dissipating, which is why Dodge required the Anywhere Key to escape his imprisonment therein.
This powerful tool allowed him to leave the Wellhouse without technically crossing its threshold, and thus avoid being wiped from existence.
In the comic books, it has been theorised by one of the Locke's ancestors that Echos do not appreciate being summoned to the mortal plane as it tears them away from the afterlife.
Locke and Key seasons 1-2 are streaming now on Netflix. Read our guides to the best series on Netflix and the best movies on Netflix, check out more of our Fantasy coverage or visit our TV Guide to see what's on tonight.