Murderbot is the protagonist. It is a nongendered Imitative Human Bot Security Unit (SecUnit) that is part human clone and part robot. Murderbot does not officially have a name; team members address it as “SecUnit.” It named itself “Murderbot” because it feels guilty about an incident when it malfunctioned and killed 57 members of a mining team it was supposed to protect. Murderbot hacked its governor module so that malfunction could never happen again, and in the process, it discovered its favorite pastime: watching media. Murderbot is lax about doing its job: Any opportunity it gets, it retires to its cubicle to watch serials.

Murderbot does not trust HubSystem because it knows the company uses the cheapest software. Murderbot’s autonomy saves it from being externally controlled by GrayCris, but its distrust of HubSystem software also leads it to miss key information, like the specifics about PreservationAux and Dr. Mensah.

Murderbot is a classic introvert: Too many social interactions drain its energy. When Mensah schedules its night watch in Chapter 6, Murderbot plans “to use the time to watch some Sanctuary Moon and recharge my ability to cope with humans at close quarters without losing my mind” (110).