Ash's body language is very passive. He is gangly and tall, with his arms usually hanging at his sides, or folded in his lap. When he's not actively speaking, his facial expression remains neutral, pleasant. His skin is smooth to the touch, without callouses or even ridged fingerprints.
Martha Powell and Ash Starmer are a young couple who move to a remote house in the countryside. Ash is a social media addict and compulsively checks his phone for updates on his social network pages. The day after moving into the house, Ash is killed returning the hired van. At the funeral, Martha's friend Sarah tells her about a new online service that lets people stay in touch with the deceased. By using all of his past online communications and social media profiles, a new "Ash" can be created virtually. Martha rejects the idea outright, but Sarah signs Martha up to the service anyway, without telling her. When Martha is sent an e-mail supposedly from Ash, she furiously confronts Sarah, who urges her to at least give the service a try before dismissing it.
Over the following days, Martha is overwhelmed by grief, and soon discovers that she is pregnant. Becoming emotionally unstable, she responds to the artificial Ash's e-mail. She starts to communicate with him through instant messaging, and informs him of the pregnancy. She then uploads videos and photos of Ash to the service's database, and the service duplicates Ash's voice to talk to Martha over the phone. Martha allows herself to believe that she is talking to her dead partner, and over the following weeks she talks to the artificial Ash almost non-stop, keeping him updated regarding the pregnancy. After Martha accidentally damages her phone and has a panic attack when she temporarily loses contact with the service, the artificial Ash tells her about the service's next stage, which is still in its experimental phase: a body made of synthetic flesh that the program can be uploaded onto.
Martha buys a blank, synthetic body from the service, and following the artificial Ash's instructions she allows the body to take on Ash's physical characteristics. The end result is a clone that looks almost exactly like Ash, only missing minor characteristics such as his facial hair and a mole on his neck. From the moment the clone is activated, Martha is uncomfortable and struggles to accept its existence. Despite the clone satisfying her sexually, she quickly becomes frustrated by Ash constantly doing what she says without question, its lack of emotion (only expressing emotions when she tells it to do so), and the absence of certain habits and personality traits which the real Ash had but the service did not have information on. After an argument, Martha decides she can no longer tolerate the Ash clone, taking him to the edge of a tall cliff and ordering him to jump off. The clone agrees to do so, but Martha grows even angrier, saying that the real Ash would not have willingly jumped. The clone responds by begging for its own life, causing Martha to realise that she can't bring herself to get rid of it.
The scene cuts to several years later, and Martha is shown to have raised her daughter Emily in the country house, keeping the Ash clone locked in the attic. She allows her daughter to see the clone on weekends, but the daughter convinces Martha to allow her into the attic on her birthday to give him a piece of birthday cake. Emily reveals in her conversation with the clone that she knows it does not need to eat, and merely used this as a ruse to get extra cake; he compliments her guile. While her daughter is in the attic with the clone, Martha waits at the bottom of the attic steps close to tears, then after regaining her emotional composure, she climbs the ladder to join them.
On the surface, Ash's personality is quite bland, only displaying emotions when he is told or given permission to. He is focused on sensing the feelings of those around him, and trying to react accordingly. He does have a sense of humor, as the real Ash did, but he has a limited knowledge of how to behave, and can sometimes say or do the wrong thing. When he makes a misstep, he asks for correction, and learns from it, acting correctly the next time the situation arises. Of course, his only teacher has been Martha (and to a lesser extent her daughter), so he's used to her particular way of doing things.
Being around Ash for a short time, one might not immediately tell that he isn't "real." But spend a prolonged amount of time with him, and the difference becomes not only apparent, but disturbing, entering Uncanny Valley territory. He was created for the purpose of providing companionship to a grieving person, and doesn't know how to function in any other context. Additionally, in his case, that person decided she could hardly bear the sight of him after just a few days in his presence, and locked him in the attic for the rest of his unnatural life. Ash has spent the better part of the last decade alone, and as such is somewhat out of practice in dealing with people.
Ash is an odd mix of child and adult, in that he's only existed for about a decade, and so only has a child's worth of experiences, but he possesses an adult's body, brain, and social expectations. No one will look at him and treat him like he's only eleven years old, even though technically he is. They will expect him to know how to behave as an adult, even though there are many things he's never done that normal adults have. Although he has access to the real Ash’s memories and experiences— or at least those that were captured on social media— they are an archive he can reference rather than his own real lived experience.
It is unclear whether Ash feels genuine emotions such as fear, amusement, or love, or whether he's merely parroting back what his programming tells him is the appropriate response to the given stimuli. However, his expression of emotions is as close to true feeling as he can get. One thing he can genuinely feel is confusion. When faced with a query or a stimulus that he cannot parse, he doesn't know how to react. His first instinct is to ask the person to repeat their question, or redefine the parameters of their request. This shows how he is basically just a computer with legs. If the code is broken somewhere, the program will not run.
Having spent the past decade-ish of his "life" locked in an attic, only seeing two people (and only then quite rarely), Ash has become lonely. He enjoys making conversation and being social, as the real Ash was a very sociable person, constantly talking to people on his phone and listening to the news. Ash as he exists now still longs to connect to people, he has just been unable to as he couldn't leave Martha. He'll be eager to see new places and meet new people, have new experiences, and be able to learn and grow.
Ash may have better luck with strangers than he did with Martha, because Martha judges him against her feelings for, memories of, and associations with the real Ash. He couldn’t possibly match up to his perfect example. When faced with people who never knew Ash as he was when he was alive, clone Ash has a much better chance of being accepted, despite his quirks and shortcomings. Perhaps this is one reason Martha's daughter seems to have less trouble interacting with Ash than Martha does; because she never knew her father.
As an android, Ash does not need to eat, drink, sleep, blink, or breathe (though he can appear to do so if it would make the people around him feel more comfortable). His body is completely synthetic, and also comes with the following features: