"Nerissa's Seal" is the first issue in the Arc 2: Nerissa's Revenge Saga, and the number sixteen overall issue of W.I.T.C.H.
Will, Taranee, Cornelia and Hay Lin go on vacation with Irma and her family to the beach to have some fun in the sun. However, their fun doesn't last long because soon enough the W.I.T.C.H. girls are called away to Kandrakar where Yan Lin informs them about a previous guardian named Nerissa and tells them that she will be their new enemy. Meanwhile, at Mount Thanos, Nerissa uses her powers to transform a dog into her minion Khor and sends it off to do battle with the W.I.T.C.H. girls and capture Hay Lin.