The speaker describes looking blank and distant on the outside while a lot is going on within. They say the emotionless act is self-defense, and they picture their mind as a wall of thick barbed wire. That image shows how protection and isolation come together: the wire keeps others out, but it also keeps the speaker in. They admit to pushing people away even though they want them to stay, and the poem suggests that letting anyone close feels risky, almost like "a crime."
Writing is the speaker's way of getting troubling thoughts out of their head. These thoughts are called "Demons," and they seem to want the speaker dead. The mood is guarded and heavy, with a dark undercurrent. The ending shifts the tone, though. Telling the reader not to worry, the speaker claims to be the Demons' "Leader" who runs the "Enterprise." That line reads as an attempt to take back control, offering a note of defiance and strength after all the fear.