I think it's pretty obvious it's about PMS. When I first heard the chorus, I laughed out loud so hard. Very smooth, Billie XD I think the narrator is confused about how his lover/'Mary' is acting (as most men are loll) during her "hour of darkness". He doesn't know how to interpret her behavior, or if she really is upset or it's just her "red tide". Hence the line "Is this passion or... Or your red tide?" She may be moody and distant now ("Mary's breaking your kiss goodnight"), but it will pass, and she still loves him ("This is where her heart will not die", meaning his kiss/lips).
I think it's pretty obvious it's about PMS. When I first heard the chorus, I laughed out loud so hard. Very smooth, Billie XD I think the narrator is confused about how his lover/'Mary' is acting (as most men are loll) during her "hour of darkness". He doesn't know how to interpret her behavior, or if she really is upset or it's just her "red tide". Hence the line "Is this passion or... Or your red tide?" She may be moody and distant now ("Mary's breaking your kiss goodnight"), but it will pass, and she still loves him ("This is where her heart will not die", meaning his kiss/lips).