with the fairies

away with the fairies

Seeming eccentric, distracted, or a bit crazy. I can't follow what your mom is talking about—it's like she's away with the fairies all of a sudden.
See also: away, fairy

(away) with the fairies

giving the impression of being mad, distracted, or in a dreamworld.
See also: fairy
References in classic literature ?
The best proof of this was his caution with the fairies.