i think its about a relationship that one of the writers had when they were younger, before they were married. from the first verse, i'm understanding that the girl somehow passed away while they were still dating, hence the lyrics "When God took her with time, God made me quite alone" from the lyrics "i'll never let you down boy, ill never let you go" it seems like they were sure to stay together forever. the writer feels so much pain when he's seeing her 'ghost on the dance floor' and having her so close, coming from the lyrics "I saw your ghost tonight, and God it felt like Hell, to know you're almost mine"