Most poems about an enemy put the threat outside the speaker. Jay Mortimer's "Alter Ego" opens by moving it in: "she is inside me / with brittle bones / with poisonous envy." The speaker describes a double lodged in their own body, hates her, longs to be rid of her, and ends by admitting that she may never leave. The central idea is a painful paradox. You cannot evict an enemy who lives where you live, and the wish to escape is already shadowed by the fear that escape is impossible.
The first stanza builds this figure out of just two images. "Brittle bones" suggests something fragile that could snap, while "poisonous envy" suggests something that can harm others and the host as well. The pairing is odd and effective: she is weak and toxic at once. The repeated "with" makes the lines read like an inventory, and the poem never tells us what she does or whom she envies. We are given only what she is made of, which makes her feel both physical and vague. The lack of capital letters and punctuation adds to this. Nothing is fenced off, so she seems to seep through the whole poem.
In the second stanza the speaker stacks three labels on indented lines: "my enemy," "the alter-ego," "the ultimate freak show." The first is personal, the second clinical, the third cruel. "Freak show" is the most revealing, because it suggests display, staring and shame, as if the speaker feels watched or exposed by the thing inside them. "Ultimate" is a blunt, almost schoolyard superlative, and the bluntness makes the line sound raw rather than polished. There is a quiet sound-link too: "ego" and "show" end on the same long o, a near-echo that ties the two names together. The title spells the term "Alter Ego," but the body of the poem hyphenates it. That small change might hint at a self joined by a seam, though it could simply be a matter of style.
Until now the poem has avoided true rhyme. Then, in the third stanza, it arrives: "I lust for the day / when she goes away." The rhyme has a singsong, almost nursery quality, which suits a wish that sounds simple and childlike. The verb "lust" is the surprise. It is a word of hunger, and using it for the longing to be free of someone suggests the speaker is as obsessed with her absence as they are tormented by her presence. That is an inference, but the word choice supports it.
The last stanza is where the poem's construction pays off. "But I fear / I fear" stumbles. The repetition, and the line break that leaves the fear without an object, make the speaker hesitate before saying the unbearable thing. Then comes the completion: "that she will always / be here." The word "fear" rhymes with "here," so the sound repeats what the sense says. The fear and the presence are bound together, and the poem cannot finish without locking the rhyme shut. "Always" dangles at the end of its line, and "here" is the poem's final word, a small, present-tense place from which she cannot be removed. The slight extra space before "be here" on the page may even look like her sitting off to one side, apart but still in the room.
The poem is significant because it says so much in so few words. It never names what the alter ego stands for. Readers might hear an inner critic, an illness, a hated side of their own character, or something else, but the poem leaves that open, and that openness lets it fit many experiences of being at war with oneself. Its form also acts out its meaning. Free, unrhymed lines describe the problem, then a hopeful rhyme promises escape, and a second rhyme takes it away. The poem ends with a fear instead of a solution, which is what makes it feel true.