Bredon Hill

In the poem "Bredon Hill", the author described life on and around Bredon Hill in the early 20th century. He explains how he and his lover spend many of their Sunday mornings on Bredon Hill listening to the church bells ring through the valleys. As the poem progresses, we find out that his lover died and the later part of the poem describes the sorrow and loss of his lover.
In the first two stanzas, the author introduces of his lover and how happy they are being together as they spend their Sunday mornings lying on Bredon hill. They listen to the distant church bells which are pleasant to listen to and it put him in a cheerful mood. The third stanza suggests that the bells are calling them to go to church but instead, the woman decides to stay with her lover. In the fourth stanza narrator viewed the church bells as wedding bells and he states "And we will hear the chime, And come to church in time." He is saying that they will be at the church when it is time for them to get married.
In the fifth and sixth stanzas, the speaker reveals that his lover has died "and went to church alone." It means that she has gone to church alone before their time. The speaker says "My love rose up so early", meaning that his lover has gone up to heaven. In addition, the speaker used expressions like "Groom there was none to see" and "The mourners followed after", to describe the loss of his lover. In the last stanza the speaker says that the bells are still ringing but they now represent funeral bells.
The question I have in mind about the poem is when the speaker says "And stole out unbeknown". What does this mean? Is this the reason why the speaker's lover died?
I find it interesting on how the author employs the idea of the changing of seasons to describe life and death and happiness and sorrow. In the beginning it is still summer when the speaker and his lover are happily together and then it turned to winter, also a time associated with death and loneliness; his lover