What is the inciting incident in Susan Glaspell's Trifles?

The inciting moment of a play, also known as its catalyst, is the the event which propels the protagonist into action.

The inciting moment of Trifles occurs when Mr. Hale, who is neighbors with John and Minnie Wright, stops by to speak with John. Upon entering the house, he finds Minnie in a chair, "rockin' back and forth." She informs Mr. Hale that her husband is dead because of a "rope around his neck." She maintains that although she was sleeping in the bed beside him at the time of his death, she has no idea who killed him.

This moment when Minnie informs Mr. Hale of her husband's death results in a flurry of activity. Minnie is arrested, and investigators arrive to inspect the home for evidence. Although she has faced previous struggles with her husband, now Minnie is fighting for her freedom and possibly for her life. The struggle to evade legal repercussions for her actions will be fought in her absence since she is imprisoned. Mr. Hale's wife also arrives, and she and Mrs. Peters discover that Minnie seemingly lived a dismal existence, enduring the abuse of her husband. As the men investigate upstairs, the women quickly decide to protect Minnie after finding evidence of the injustices she has suffered.

What are the significant untold dramatic questions in Susan Glaspell's one-act play, Trifles?

Well, the biggest question that the play begins with and is subsequently answered by Mrs. Hale and Mrs. Peters, is what precisely happened to John Wright and who killed him. It is clear that the play begins with something of a mystery. Hale begins by narrating to the County Attorney and to the rest of the characters what happened when he came to the house and how he saw Minnie Wright sitting on the chair, looking "queer". She then tells Hale that Mr. Wright had died:

"He died of a rope around his neck," says she, and just went on pleatin' at her apron. Well, I went out and called Harry. I thought I might - need help. We went upstairs, and there he was - lying' -

Mrs. Wright then tells Hale the somewhat suspicious story that she did not know who killed her husband, and that she slept through the murder. The rest of the play presents the male characters' bumbling attempts to find out what happened, whilst the women, disparagingly dismissed by the menfolk, piece together the motive with ease and prove who the murderer was - only to hide the truth.

What is the definitive moment in the play Trifles by Susan Glaspell?

The clear definitive moment in the play comes when both Mrs. Hale and Mrs. Peters realise that the dead bird they have found is the one piece of evidence that definitely links Minnie Wright to the murder of her husband. Although Mrs. Peters pretends that this dead bird is actually unimportant, at the same time as she tries to state this opinion, the County Attorney is heard saying the following:

If there was some definite thing. Something to show--something to make a story about--a thing that would connect up with this strange way of doing it.

What both Mrs. Hale and Mrs. Peters realise at that precise moment is that they have discovered precisely that "definite thing" that the County Attorney is looking for, and it is the dead bird that would allow him to "connect up" and "make a story" about the death of John Wright, allowing Minnie to be convicted with his murder. This part of the play is so climactic precisely because the women realise that what they do or do not do will have profound ramifications for Minnie and result in her imprisonment or her freedom. As she has actually been imprisoned for all of her married life, their actions are designed to give her freedom, as in an act of female solidarity, the two women act to hide the dead bird.

How does the discovery of quilt pieces advance the plot in Susan Glaspell's Trifles?

In Susan Glaspell's Trifles, the dead canary that Mrs. Hale and Mrs. Peters find does two very important things in terms of galvanizing the plot.

Up until this point in the play, Mrs. Hale is uncertain as to Minnie Wright's guilt in the alleged murder of her husband, while Mrs. Peters is very much in line with the letter of the law. Mrs. Hale is the more sympathetic of the two women at the play's beginning. However, as the women listen to the chauvinistic remarks of the men (women worry over "trifles," the very things that keep a house going—bellies filled, and clothes and homes cleaned...hard work), there is a noticeable change in Mrs. Hale's attitude, who actually speaks up to defend a woman's worth in the home. This foreshadows her eventual change of attitude with regard to Minnie's plight.

HALE. Well, women are used to worrying over trifles. 
(The two women move a little closer together.)

COUNTY ATTORNEY ...And yet, for all their worries, what would we do without the ladies? (...Starts to wipe [his hands] on the roller towel, turns it for a cleaner place.) Dirty towels!...Not much of a housekeeper, would you say, ladies?

MRS. HALE. (stiffly). There's a great deal of work to be done on a farm.

COUNTY ATTORNEY. To be sure. And yet...I know there are some Dickson county farmhouses which do not have such roller towels...

MRS. HALE. Those towels get dirty awful quick. Men's hands aren't always as clean as they might be.

COUNTY ATTORNEY. Ah, loyal to your sex, I see.

(The attorney's last comment also foreshadows the women's eventual support of Minnie Wright.)

The women gather some things to take to Mrs. Wright in the jail. Then they discover first an empty birdcage, worse for wear:

MRS. PETER. Why, here's a birdcage. Did she have a bird, Mrs. Hale?

MRS. HALE. Why, I don't know whether she did or not--I've not been here for so long. There was a man around last year selling canaries cheap, but I don't know as she took one; maybe she did...

MRS. PETERS. (examining the cage). Why, look at this door. It's broke. One hinge is pulled apart.

MRS. HALE. (looking, too.) Looks as if someone must have been rough with it.

Here is the first sign of John Wright's anger, something Mrs. Hale had noticed missing before. Then they find the bird:

MRS. HALE (lifting the silk.) Oh, Mrs. Peters--it's--

MRS. PETERS. It's the bird.

MRS. HALE. But, Mrs. Peters--look at it. Its neck! Look at its neck! It's all--other side to.

MRS. PETERS. Somebody--wrung--its neck. 
(Their eyes meet. A look of growing comprehension of horror...Mrs. Hale slips box under quilt pieces, and sinks into her chair...)

This is a moment of enormous significance for the women: they have found proof of John Wright's brutal nature, but they have also found evidence that could lead to Mrs. Wright's conviction for murder. Finally understanding what Minnie had to live with—we can infer that he was also abusive with Minnie—the women choose to say nothing. The men have made it clear that they believe a woman's day is spent dealing with "trifles," unimportant things—rather than extremely hard work that makes up a woman's entire life. Certainly they won't understand Minnie's despair not at being brutalized herself, but seeing the only joy in her life, the singing bird (symbolic of Minnie herself), broken in another of John's fits of anger—for although she has been married for years, it seems the bird's death breaks her. 

The bird marks the turning point in the play.