One night between sunset and river
On the old bridge we stood, you and I.
Will you ever forget it, I queried,
- That particular swift that went by?
And you answered, so earnestly: Never!
And what sobs made us suddenly shiver,
What a cry life emitted in flight!
Till we die, till tomorrow, for ever,
You and I on the old bridge one night. ("The Gift," Chapter Two)
As to Lucette's ancestry, Van tells us (and I don't see why we should disbelieve him) that she is Dan's own daughter (1.1).