Lena Terhaar's poem is about a woman who hides her suffering so well that most people never notice it. She cries alone, in dark corners where no one will see, and the poem follows her tears from her eyes down to her chin as if they leave a visible trail. The speaker seems to understand her deeply, and the tone is gentle and sympathetic rather than judging.
The poem suggests this pain has built up over a long time: "years upon years." Her past leaves scars under her clothes, which the speaker calls "a roadmap to places that nobody knows." That image makes her hurt feel both physical and private, a whole history no one has been shown. Meanwhile, she looks happy to everyone else, which is the "disguise" of the title.
The mood is quiet, sad, and a little urgent. The last lines ask us to look more closely, because the truth is there in her eyes for anyone who bothers to see it.