In Daphne du Maurier's novel, Rebecca, there is an inquest because Rebecca's body is found in her boat which sank to the bottom of the bay. Maxim had erroneously identified the body of another dead woman as his wife, eight months earlier when Rebecca died.
The inquest is particularly important because it seems that there was foul play: someone had punched holes in the bottom on her boat and seemingly she had been trapped on the boat when it sank.
This is ironic because the inquest is carried out to investigate her murder—which she most probably arranged that her husband commit, knowing that she was dying from cancer. A mean-spirited, unfaithful wife, she had told Maxim that she was having another man's baby and was going to force him to raise the child as his own. In a fit of rage, Maxim kills Rebecca. Learning later that she was not pregnant, it would not be out of character (he believes) for her to arrange for Maxim to kill her so that she could have the satisfaction of knowing while dying that she had at the least left him with terrible guilt, or perhaps even more, destroyed his life as well.
However, the inquest proves quite the opposite—the authorities come to the conclusion that knowing that she was going to die a slow and painful death, Rebecca committed suicide. In essence, she did commit suicide—choosing to die at her husband's hands. However, the acts that she perpetrated in order to punish Maxim do not come to fruition, and he is exonerated from having any hand in her death. This is ironic because he was fully involved in her death, but no one believed what she had tried to manipulate others into believing about her husband.
The beginning of the story describes a dream the narrator had of the Manderly of the past. Her description of nature seems to describe the person of Rebecca (and acted as foreshadowing to what the new Mrs. de Winter was to discover):
Nature had come into her own again and, little by, little, in her stealthy, insidious way had encroached upon the drive with long tenacious fingers. The woods, always a menace even in the past, had triumphed in the end.
The inquest is conducted to learn about the cause of Rebecca's death. Her death was ultimately caused by her unwillingness to follow what life had "dealt" her, refusing to back down—even as the land surrounding her home refused to be conquered. However, where the woods "triumphed," Rebecca did not.