"All Emily Windsnap wants to do is impress her best friend, Shona, and the other mermaids who live in the sea around Allpoints Island. But instead, she wakes up with the kraken, a terrifying octopus-like monster the size of an apartment building. Now he's coming after everything and everyone, and it's up to Emily to stop him. Luckily she's got help from Shona and one other person--someone Emily hoped never, ever to see again."--Back cover.

When Neptune tells Emily and her merman father and human mother to return to Brightport to try to make merpeople and humans work more closely together, Emily faces problems with old enemies, her new, half-merfolk friend Aaron, and a mystery related to a group of legendary lost sirens.

A class trip to a beautiful island is overshadowed by a local myth about a mysterious ship that may have ties to the lost city of Atlantis.

"Traveling home by cruise ship should be a relaxing break after Emily's latest adventure, but things take a turn when the ship is overtaken by a pirate king and his crew. After the pirates collect everyone's riches, they steal something even more valuable: Aaron. The pirate king's eldest son takes Aaron captive, forcing him to help guide the pirates to the mythical Trident's Treasure. So Emily dives into action and joins the younger son's crew in...