An immortal of wealth and influence, he was arrogant and selfish in the extreme, he did not love but possessed.
In the 19th century, he took Grace Chandel to the Amazon so she could work on her medical research. Duncan warned her that once Carlo thought something was his, he never gave it up. Carlo confirmed this by telling MacLeod, "She's mine now, and always will be."
He was a self important man who could not conceive that Grace, who was his lover for a century, could stop loving him. She ran from him, changing her identity three times to lose him at one point. "He went from being an explorer to being a conqueror. He started terrorizing and dominating the people I was treating He demanded whole villages worship him like a god. I've been running ever since. Every few decades he finds me."
He caught up to her again in Paris where she was working on medical research on an anti-viral vaccine with her mortal husband Paul. Sendaro shot Paul and burned their lab, planting the murder weapon in Grace's apartment. He intercepted her and Tessa on their way to sanctuary with Darius at his church. Darius allowed them to speak alone in the church.
Carlo said, "You loved me once, I could make you love me again." She said he could not, and accused him of Paul's murder. He, of course, denied it. He said she had no future with the police looking for her, that she cold hide on his estate in the Amazon for 20 or 30 years. She scorned him, and he walked out with a final threat to MacLeod. He felt threatened by MacLeod and when the man came to Carlo's old home, the two dueled briefly until Grace left with MacLeod. "Grace, there is no way you can escape me!"
He intercepted her again, as she left Darius and was accosted by police. Carlo put down two cops and was then shot down by Lebrun, While Lebrun called for an ambulance, Carlo recovered and then beat the man unconscious, taking Grace with him, dragging her to the Metro with MacLeod in pursuit. Grace slugged him and ran off down the tracks, the two men behind her until they stopped to fight it out. He trapped MacLeod's foot between tracks by pulling a switching lever and advanced with his blade to take the Highlander's head. MacLeod continued to defend himself, throwing his coat into Carlo's face. As the man pulled it away, his blade came in contact with the live rail, electrocuting him. He fell on the tracks to be beheaded by the next train, his quickening going to the nearest Immortal: MacLeod.
Trivia - The name Carlo Sendaro in fact isn`t Portuguese: the most similar form in Camões language would have been Carlos Sendeiro.