Love is a like a garden, Rarity had always known that. You had to take care of the garden that was love: water it with affection, weed out petty fears, nurture the timid intimacies. But the weeds that suffocate the flowers and feast on the trees can strike with little warning even when the utmost care is taken. The rot of despair can eat away at the green no matter how much love is poured into a relationship.
Rainbow deals with the possibility of a flightless future in the aftermath of a brush with death with help from Rarity. Many waters cannot quench love; perhaps not even crippled wings can dampen it for long.
(Sequel to Where the Sun is Silent. You do not really have to have read that story to enjoy this one. Know only that Rainbow and company were pawns in the sick games of an elder god of chaos and that she was seriously injured.)