Beautiful butterfly in my home - help!

[TheGreatSloth]

Very weirdly, I have just found a beautiful orange and black butterfly in my bedroom.
The windows have been shut all day so I have no idea where it has come from. (Though oddly I did find a tiny baby bird in here a day or so ago - very small with soft brown feathers - can there be something in my loft?)
Anyway, what should I do? My first thought was to put it out but its freezing outside. Will it die?
For now I have just put out a saucer of water with a bit of sugar in it, on a table, but what should I do? I do not want to kill it, but cannot really set up as a butterfly house.

Some butterflies hibernate in houses, so you might have a guest for the next few months!

If so it won't be any bother, will just sit there until Spring.

Have you a shed or garage?

scottishwildlifetrust.org.uk/2013/11/butterflies-hibernating-in-houses/

I had one last week and I seen online to put it in garage

Thanks so much. Mine is clearly a Red Admiral. The advice on the link is to put it in a cardboard box to calm down, then relocate to the shed. Should you keep it in the box in the shed? I’m thinking maybe release it in the shed (not in the box) with some saucers of water & sugar in case it doesn’t hibernate immediately?