In the meantime, Sheriff Marshall discovers that Timothy Flynn’s wife had cowpox on her hands. When they go to excavate the bodies, they discover that one of them has the letter ‘B’ branded on their skin.

“I think we need a word with Billy Myers,” says the sheriff.

Although we aren’t told why Billy is such an important element in this story, we can clearly see his name across all things. Scarred and claimed, on both skin and reputation.

Later that night, Billy’s son finds him roped and hung. In the distance, an unknown rider escapes.

Meanwhile, Cornelia (Emily Blunt) is still on her quest to return the young rescued children to the Mennonites. She has comes across a scientist by the name of Jenson, who is showing her a sample of cells developed from a tick bite.

Jensen explains how ticks work – how the parasite invades the body and can wipe out an entire herd of cattle. He ponders how strange it is, how such a small thing can do so much damage.

Cornelia asks if he is looking for a way to treat it.

“Nature, red in tooth and claw,” he tells her, misquoting Tennyson for Darwin.

He tells her that this is the key to treating such a thing: by taking the parasite, killing it, and putting it back in the body, he hopes that this method could be applied to all aspects of life.

Cornelia is shaken when he includes the acculturation of Indians in this methodology, telling her:

“If you wanna survive in the white man’s world, you have to become one.”

When Jenson goes to leave, he is suddenly struck by a bullet, killed instantly. Cornelia plays dead as a Native American man comes down. However, he leaves her be, telling her that he only shot Jenson because he was wandering where he was not supposed to be.

It seems that this time, Jenson was the parasite.

Everyone is as a parasite in the third and most intriguing episode of BBC Two’s The English