Columbine: Emily Windsnap and the Castle in the Mist is the third in the series about the young half-mermaid.

This book starts right back at the time of Neptune’s wedding. He and his human bride exchange rings, a diamond ring representing the earth, a pearl ring representing the sea, symbols of the harmonious union between the two. Neptune magically enchants the rings so that they can only be worn by a happy mer/human couple, or their child.

Both rings are believed to have been lost since the disastrous ending of the marriage, but when Emily Windsnap finds the diamond ring buried in the sand after the affair with the monster, they realize the Kraken must have had it all the time. Neptune wants the ring back, but Emily cannot take it off – part of the enchantment. Neptune’s fury creates a storm which transports Emily and her boat far away to the castle in the mist, where she finds another semi-mer and learns the secret power of the rings.