What is the theme in Mortal Fear by Greg Iles?

The desire for immortality is the main theme. Edward Berkmann's desire for immortality leads him in two different directions. He first tries to gain immortality by perfecting a procedure to transplant the pineal gland from a young donor to an older recipient. He takes the limited knowledge he has from a study done on mice. In that study, the mice that were given the transplants acted younger, exhibited renewed vitality and were more interested in sex. It's noted that they didn't really grow old be eventually just died.