Story; After the final battles for both Buffy and Angel, They were finally able to live normal lives. They went on leading separate lives until Buffy finds out she is dying and go to see Angel. Angel and her reminisce and reconnect.
Why won't you diiiiiiiiiiie?
Your Blood in miiiiiiiiiiiine
We'll be fiiiiiiiiiiine
Then your body will be miiiiiiiiiine
Pretty much sum's up Angelus's intentions toward Buffy. ;-)