Three short lines, and the speaker is already cornered. The central feeling is fear, but the odd thing is where it comes from: the speaker is frightened of themselves. Whatever scares them isn't outside the room. It's their own thoughts, memories, or impulses, and that is why "there is no escape." You can run from a stranger, but not from yourself.
The title adds a layer. "Two Can Keep A Secret" echoes the familiar saying that two people can keep a secret only if one of them is dead. Here, the "two" might be the speaker and their own self, sharing something buried that neither can get rid of. That is an inference, but it fits the poem's tight, claustrophobic feel. The lowercase "i" and the abrupt line breaks make the voice sound small and breathless. The mood is uneasy and confined, and the poem ends on its bleakest note, leaving the reader without comfort or resolution.