After a night out at a club the body of club promoter, Miguel Martinez, was discovered stabbed to death in his apartment. Since Miguel was a Spanish citizen, and the son of a diplomat a crime lab supervisor from Barcelona, Hector Vargas, had flown over to assist with the case. Mack dismissed Hector from the crime scene once he learned that the victim was Hector's nephew.
The CSI interviewed the victim's girlfriend, Natalia Sanchez, at the Spanish consulate. She had found the body and immediately called the victim's mother in Spain who had advised her to go to the consulate, and told Natalia that she would take care of everything.
The evidence found at the scene and on the body made Mack question whether or not the death was a homicide. Further investigation revealed that Miguel had fought with a drug dealer at his club, but the dealer denied having anything to do with Miguel's murder.
A recovered piece of solar paneling and a single drop of blood led detectives to a vagrant with a record for stealing solar paneling. The homeless man revealed that he had been in Miguel's apartment, and that Miguel had paid him to murder him. However, the vagrant couldn't go through with it.
The knife used to stab Miguel was found several blocks from his apartment, but after Mack and Hector Vargas had taken a second look at the crime scene they discovered evidence that proved Miguel had killed himself.
Natalia confessed that Miguel had asked her to cover-up his suicide so that his mother wouldn’t know. She had had second thoughts about helping him, but arrived too late to stop Miguel from going through with the planned suicide, and decided to follow through with the cover-up as Miguel had asked her.