The draft poem, called "Last Letter," describes Hughes' anguish in the days leading up to Plath's death in her London home on February 11, 1963. Beginning with "What happened that night? Your final night," it ends with the moment Hughes is informed of his wife's death.
Hughes had never so directly written about Plath's suicide. The New Statesman magazine, which published the drafts Thursday, called the abandoned poem an important missing piece in Hughes' collection "Birthday Letters" the only place readers have so far been able to find explicit references in Hughes' work to the tragedy.
The doomed romance of Hughes and Plath, both celebrated poets, continues to fascinate the literary world. Plath, an American writer, married Hughes in 1956 then struggled with depression and the difficulties of balancing her literary ambitions with domestic life. She committed suicide by carbon monoxide poisoning at age 30.
Hughes, who had two later marriages, went on to become poet laureate from 1984 until his death. He didn't speak out about Plath's suicide until the anthology "Birthday Letters" was published in 1998, just months before he died.
"Last Letter" described Hughes' pained reaction when a phone call broke the news of Plath's death.
"Then a voice like a selected weapon/ or a carefully measured injection/ coolly delivered its four words deep into my ear," Hughes wrote in one version of the drafts.
"Your wife is dead."
Hughes was separated but still married to Plath when she died, leaving behind their two young children.
Several drafts of the poem are held in the British Library's archives, which bought it from Hughes' third wife, Carol Hughes. The poem is believed to have been written in the early 1970s.
Carol Ann Duffy, Britain's current poet laureate, called it the "darkest poem [Hughes] has ever written."