What does the underlined sentence mean?

Reading Comprehension: Read the quoted parts carefully and answer the questions.For a long while we just stood there, looking down at the profound and fleshless grin. The body had apparently once lain in the attitude of an embrace, but now the long sleep that outlasts love, that conquers even the grimace of love, had cuckolded him. What was left of him, rotted beneath what was left of the night-shirt, had become inextricable from the bed in which he lay; and upon him and upon the pillow beside him lay that even coating of the patient and biding dust.

What does the underlined sentence mean?
【正确答案】：

EMILY HAS BEEN SLEEPING WITH THE DEAD BODY, WHICH MADE HIM THE MAN WHOSE WIFE HAS COMMITTED ADULTERY.

【题目解析】：艾米丽一直和一具尸体共眠，这让他成为一个妻子和别人通奸的男人。