The Viking’s Wife Finds the Frog.
. . . When she awoke, a little before sunrise, what was her grief to find the child gone! Dressing in haste, and lighting a pine torch, she found the place of the child had been taken by a great ugly frog!
Filled with fear, she seized a stick to kill the frog; but it looked at her with such sad, gentle eyes that she could not bring herself to do it.
Moving to a closed shutter, she opened it to let in the light of day. Just at that moment the sun rose. Its beams fell on the frog, and lo! the wide mouth became smaller, the limbs grew rounder, and instead of the frog there lay her dear little baby once more!
‘What is this?’ cried the lady. ‘Have I been dreaming?’
Lifting up the child, she pressed it to her heart; but the little one fought and bit like a wild cat.
Before many days had passed, it was plain to the lady that the child was under a spell. During the day it was as lovely as a little fairy, but had a fearful temper; during the night it was a frog, with sad and gentle eyes.
From the Story: The Marsh King’s Daughter.
Hans Andersen’s Fairy Tales.
By William Woodburn.
Illustrated by Gordon Robinson.
W. & R. Chambers, Limited: London & Edinburgh. 1917.
Elephant's Picture Book 
I remember this story and love it. I like the look of startled horror she has and also her dropped waist 20’s style dress. I know this illustration is a little earlier than that but certainly looks contemporary with the time it was published.
And the frog is certainly captured just right, I think!
I like her dropped waist Viking dress too! The frog would be hard to get rid of with its sweet sad eyes . . . maybe not so much the baby that kicks and screams all day!
Elephant