SirenPhillipshaslivedherlifethinkingshesanordinarygirl,inanordinarytown.Ontheeveofhertwelfthbirthday,however,shelearnsthatsheisfarfromordinary.DestinedtoturnintoaMermaidattheageoftwelve,Sirenmuststrugglewithhernewreality,sayinggood-byetohermotherandfriends,whileshetransitionsintothewater.Tomakemattersworse,agroupofhuntersaretryingtocatchher.ShesoonbecomesfriendswithAdamWilts,anewboyatschool,whosheturnstoforhelp.Heagreestohelpher,butfindshimselfcaughtinthemiddle,whenitshisownfatherwhoisafterSiren.WhenSirensmotheristaken,thetownmustrallybehindher,andhelphermakeapeacefultransitionintothewater,beforethehunterscanfindoutwheresheis.