In a tragic example of situational irony, Phyllis gives up the possibility of true love with Matthäus in order to remain loyal to Humphrey (the man she is engaged to), only to find out that Humphrey has chosen true love with someone else over loyalty to her. The following passage demonstrates the painstaking process that Phyllis goes through to decide to stay with Humphrey:
Without [Matthäus] her life seemed a dreary prospect, yet the more she looked at his proposal the more she feared to accept it—so wild as it was, so vague, so venturesome. She had promised Humphrey Gould, and it was only his assumed faithlessness which had led her to treat that promise as nought […] [H]er promise must be kept, and esteem must take the place of love. She would preserve her self-respect. She would stay at home, and marry him, and suffer.
This peek into Phyllis’s mind sets up the tragedy of the ironic twist. She is aware that marrying Humphrey is “a dreary prospect” that would lead her to “suffer,” and yet she feels she must “keep her promise to him,” incorrectly assuming that he has kept his promise to her after misinterpreting something she overheard him say when he arrived back in Dorset.
When Phyllis learns that Humphrey has not kept his promise to her, she simultaneously feels relief and immense grief, as she realizes that she has given up a future with Matthäus for nothing. Though Phyllis was loyal to Humphrey on the surface, her heart remains loyal to Matthäus (even after his untimely death).