Since "Bones" season 10 wrapped up last June, much has been speculated about the show's direction. Last August, TV Line has reported that the show's creators have re-written the whole plot for season 11, and actor David Boreanaz, who plays one of the lead roles, will not be in it. The website reported that the 46-year-old actor has "suffered a bad reaction to an antibiotic," and needed time to recuperate.

But Boreanaz, who portrays FBI Special Agent Seeley Booth, was quick to jump back on board and confirmed his return for the next season.

"Nothing matters to me more than Bones, so I was thrilled when the producers came up with a way for me to take a few extra weeks to recover from a personal health issue without delaying production," he wrote in a statement for TV Line. "I'm happy to say that I'm now feeling great and will be back to work tomorrow, and that our 11th season premiere will broadcast on schedule - with me in it." 

However, Boreanaz' sickness may not be as mild as an allergic reaction. Radar Online reported that the actor has been arriving on set looking "frail and weak," and worried producers have already re-worked the scenes to hide his illness.

What could be the actor's mystery illness?

Radar Online's sources revealed that Boreanaz might be suffering from jaundice.

According to Medicine.net, Jaundice is a yellowish discoloration of the skin, mucous membranes, and the white of the eyes. Symptoms also include fever, nausea, weight loss, and weakness. While it's not a disease in itself, jaundice is a sign of underlying medical conditions, some of which could be serious and potentially life-threatening.

"Bones" will be returning on Fox for its eleventh season this Oct. 1.