John Keats composed this poem while sitting in his garden under a plum tree in Hampstead. The Nightingale song inspired the poet, which helped him complete the poem in a day. The poet starts the poem in a sad mood and explains how his “heart aches” as if he is drugged or poisoned. He felt like he drank water from the Lethe and was drowsy. It is then revealed that the song of the Nightingale is the main reason for the happiness of the poet. Finally, the Nightingale is addressed by the poet that his happiness lies in the happiness of the bird.