It's Saint Valentine's Day and love is in the air. Ulrich forgets, so at last minute writes a poem for Yumi. However, when William presents Yumi with flowers, Ulrich gets jealous and reads the poem to Sissi instead, hoping to elicit jealousy from Yumi. The two end up in a fight, both bothered and wondering if the other really likes them. Also, a man possessed by Xana leaves a necklace at Aelita's door, Aelita is convinced that it was Jeremie who got it for her. Since Jeremie didn't actually get it, he's left to wonder who did, and ends up suspecting Odd, who avoids the question. This puts the two at odds, so to speak. Meanwhile, Aelita's necklace takes control of her and forces her to deliver herself to the Scyphozoa. Luckily, Odd arrives in time, and is able to save Aelita from the Scyphozoa by "threatening" to kill her.

El Dia dels Enamorats no comença gaire bé: l'Ulrich i la Yumi s'han discutit per culpa d'en William i l'Aelita ha rebut un collaret molt bonic. Ella està convençuda que és d'en Jeremy, però, en realitat, és un regal enverinat del XANA. Quan se'l posi, no podrà evitar la temptació de tornar a Lyoko...

今天是情人节，空气中弥漫着爱的气息。Ulrich 忘记了，于是为 Yumi 写了一首诗。然而，当 William 送花给 Yumi 时，Ulrich 吃醋了，他把诗读给 Sissi 听，希望引起 Yumi 的嫉妒。两人最终吵了起来，不知道对方是否真的喜欢自己。另外，一个被 Xana 附身的人在 Aelita 家门口留下了一条项链...

C'est la Saint-Valentin ! Yumi et Ulrich se disputent au sujet de William. Aelita reçoit un joli collier et pense que c'est Jérémie qui le lui a offert en cadeau.

No Dia dos Namorados, Yumi e Ulrich discutem sobre William, e Aelita recebe um bonito colar que pensa ter sido oferecido por Jeremy.

¡Es el Día de San Valentín! Yumi y Ulrich discuten sobre William. Aelita recibe un bonito collar y cree que fue Jérémie quien se lo regaló.