PALM DESERT, Calif. -

If you've traveled on the westbound 86 Expressway, near Dillon Road, you may have spotted a new billboard, with a mother's plea for help. The case of a missing Palm Springs man remains a mystery, nearly 4 years after his truck was found abandoned, in a Thermal orchard. Marina Karas of Palm Desert tells us, "I would say that he gave me the best years of my life and I gave him the best years of his life and now it's over."

Karas had nothing but high hopes for her 21 year-old son, Spencer. She says, "To be successful, married, children. To be happy and safe."

Almost 4 years after the last time she saw him, she remembers him everyday, with a flickering candle and pictures that rest on the piano, he once played. Karas says, "His music was beautiful. He took piano lessons for 7 years and he liked the guitar."

But she says Spencer's focus shifted, once he lost his job at his church. "They had a cutback and that devastated him. And he felt left out an started going into a downward spiral."

That lead to to a path of substance abuse and hanging out with the wrong crowd. She says, "It started out with alcohol and then he got into drugs."

Karas says Spencer got into dealing drugs, when he disappeared on June 30th, 2008. His truck was found in the middle of an orchard, in Thermal. His keys, wallet and credit cards were all left inside. Since that day, Marina tells us she has received very few leads. She says, "I've only gotten two. The one boy came to my door around august and he said you know that Spencer was killed. He was shot in the head. And I just went into shock."

Sgt. Mike Kovaleff of the Palm Springs Police Department says, "We have individuals who probably have information but unfortunately they're reluctant to provide it. We keep asking them and the refuse to provide any information."

Marina says her heart tells her that her son has been killed. Not a day goes by when she doesn't wish the phone would ring with new information. That's why she has put up the new billboard, hoping someone makes the connection, picks up the telephone and gives her the information she so desperately is searching for. She says, " I want answers and I want his body, what's left of it. If it's since '08 and it's bones, then I would love to bury my son with dignity."

Until someone does reach out with a vital piece of information, Marina is left with only one thing to do. She says, "I just wait. I keep waiting."

Back in December, a hiker found skeletal remains, in the hills off of South Palm Canyon Drive. At first Marina thought they could be Spencer's, but the police department has since informed her that it's not likely, since the bones are around 10 years-old.

If you have any information on the Spencer Karas case, please call the Palm Springs Police Department at 760-323-8116 or call Crime Stoppers at 760-341-STOP.