Carlos Diaz arrives in Emmerdale in March 2000 to begin work as a chef. He immediately sets pulses racing. Carlos is introduced to Nicola Blackstock in early 2001 and the two instantly fall in love. Carlos proposes to Nicola and she accepts, however, Carlos soon begins an affair with Bernice Thomas, Nicola's half sister. Carlos has an on-off-on affair with Bernice while still was engaged to Nicola. Bernice is married to vicar Ashley Thomas during the duration of the affair with Carlos, and when Bernice falls pregnant soon after. Bernice isn't sure who the father Is, but a paternity test shows that Ashley is the father. On the day of the wedding, Carlos and Bernice decide to tell Nicola about the affair. Nicola reacts badly and attacks Carlos with her bouquet of flowers. Nicola reveals to the church about the affair, stunning her father Rodney Blackstock and Ashley. The wedding is canceled and soon after Carlos flees the village.
Carlos returns to the village, much to the shock of Nicola, who is now with fishmonger Simon Meredith. He soon learns that Bernice has left the village and decides to stay around. However, soon he decides to leave again and departs in May 2004.
In 2012, Bernice returns to the village. Nicola seems annoyed about this and when Bernice confronts her, she believes that Nicola is angry over the affair with Carlos 11 years previous. Nicola states however that she's "gotten over that" and the two rekindle. Carlos was mentioned again in 2021, 20 years after his affair with Bernice.