Other People Have Other Problems

I just read this post over at "RPG.NET" 

I think my head just exploded.

"This is my first post in this section, so usual disclaimers apply: hope I'm in the right place, etc. Also, it's a silly post, but I'd appreciate the thoughts of more experienced gamers.

So, at the start of this year I joined my wife's gaming group. It's been fun times, though it's sometimes evident that the way I'm naturally inclined to play is different than how everyone else plays. (We're playing 4e, not that I think it's overly important for the nature of the problem) They like to kill stuff, and even the paladin is kind of a morally-ambiguous hardass. My character - a crossdressing Half-Elf bard and courtesan - quickly became the conscience of the party. He put rescuing NPCs as a priority and wouldn't attack anything that wasn't obviously hostile. As I said, it's contrary to the rest of the party's motivation, but the DM assures me he likes it, as it's leading the party to do things he didn't expect (he knows the other players very well).

And this brings me to my current situation. The party encountered some unicorns that were afflicted with a kind of magical sickness that's affecting various NPCs. They were being chased. My character would have helped anyway, but in what seems to have been a genuine coincidence, he really adores unicorns. The party succeeded in saving all of the unicorns, and one of them gave birth. While the adult unicorns returned to the Feywild to seek a cure for their disease, the baby unicorns are trapped in the regular world until they reach adulthood. And my character, being who he is, swore to protect them. Now, the party's main healer is protecting two baby unicorns from things that can kill them in one hit.

From talking with the DM, this was never supposed to happen: he didn't expect the party to help the unicorns. And I'm not sure what to do here. My character can't let them die. Protecting them constantly will be to the detriment of the party as a whole, because other people need healing too. I could simply retire my character from the campaign: this would be logical, but a shame as I really enjoy playing him.

The DM has asked me what I plan to do, and is willing to discuss possible solutions, but I'm really not sure how best to approach this problem. What do you do when your character suddenly has a duty that's at odds with the main mission? For the DMs amongst you, how would you like to see this resolved if it happened in your campaign?"