The issues in the collection first appeared in 1990 and 1991. The collection first appeared in paperback and hardback in 1992.
Warning: Wikipedia contains spoilers
The fourth collection belongs with the first as perhaps one of the two collections most focussed on Morpheus himself. It begins with an Endless family meeting, which like (we assume) many Endless family meetings descends almost immediately into an Endless family argument. Desire angers Morpheus by taunting him about his intolerant treatment of a former lover, whose story formed the prologue to the second collection, The Doll's House; Death angers him further by agreeing with Desire, but Morpheus' immense respect for Death leads him eventually to agree with her assessment. He leaves his realm to travel to Hell, where he imprisoned his former lover, to release her. Having left Lucifer, lord of Hell, somewhat angry with him the last time he ventured there - in the first collection, Preludes and Nocturnes - Morpheus is understandably apprehensive about the task, but sets about it nevertheless; this is clearly one of his more basic characteristics, the belief that one should attempt to do what one believes is right.
In the event, his apprehension is somewhat misplaced. As he arrives, Lucifer is busy closing down Hell. In a beautifully illustrated sequence, Morpheus follows Lucifer around in a state of some bafflement before Lucifer finally persuades him this is not an elaborate trick, that he indeed intends to leave Hell - and his obligations as its lord - forever. His final act before leaving is to lock all the portals to Hell and cut off his wings; he then, with (one feels) a sense of some satisfaction, hands the key to Hell to Morpheus, to do with as he will. Much of the rest of the collection is concerned with Morpheus' attempt to divest himself of this troublesome piece of real estate.
To do so, he convenes all interested parties in the castle at the centre of his realm, the Dreaming. Here many characters who have parts to play later in the series are introduced, amongst them the representative of Faerie, Cluracan, and his sister Nuala. After much bargaining, wheedling, bribery, trickery, Norse drunkenness, and threatening behaviour, Morpheus manages to get rid of Hell without much harm coming to him. The collection ends with Lucifer sitting on an Australian beach, grudgingly admiring God's sunset.
The oddball issue in this mostly coherent collection is #24, "In Which the Dead Return; and Charles Rowland Concludes His Education", a rather spooky take on the traditional English boarding-school story which is used to illustrate the consequences of Hell's closure.
In places one of the more obviously comic of the series' collections, it is principally concerned with fleshing out Morpheus' nobly tragic character, and some of his history. It also introduces some of the series' more important secondary characters. These include some who play a part in the eventual denouement of the series in the ninth collection, The Kindly Ones, the Norse gods Loki, Odin and Thor. In one of the many parallel stories the collection provides Loki's particular motive for resentment against Morpheus. The start of this particular thread contains one of the key lines of the series: "There is a cavern beneath the world. (This is true. You must know in your bones that this is true, although all logic argues against it.)" It encapsulates one of the series' key ideas, a version of the philosophical idea that reality is ultimately subjective, defined by human beliefs (and, for Gaiman at least, human stories).