In the first stanza the speaker of the poem has a sudden realization, sudden light, that he has been in the same place where he is now, before. He can't pinpoint the time and place, can only sense the familiarity of the moment: the smell of grass beyond the door, the sound and the lights around the shore.
In the second stanza the speaker of the poem turns his direction towards the person with him. He talks to this person, how that person was his before as well, and again he can't pinpoint the exact time. The stanza ends with an image of the moment he experienced with this person before.
In the third stanza the speaker of the poem questions whether the current moment, with this person, happened before as well and whether it is possible, whether the time will allow them, to experience the same love again.
A notable thing to consider is the structure of the poem, each stanza is equally structured; each of the first lines in every stanza ends with the word "before"; the second line of every stanza is about "time" and the last three lines in every stanza are talking about an image or event.
