Someone needs to explain this film to me [Spoilers]

I'm usually very good at following film plots with sporadic shifts in time and seeing symbolism and how everything comes together in the end but this film just confused me to no end.

Can someone explain to me all the major plot points? Why did he kill himself in her house? Who was he? What was the point of showing her past? And what was the point in having that girl come to stay with her?

The world moves for love; it kneels before it in awe. - Edward Walker (The Village)