Chet Collins is still searching for his son since the little boy, Sean, went missing five years earlier, at the age of two. Now Chet himself is missing. The team speculate that recent activities in his personal life, combined with his continued desperation over Sean, may have ushered him into some illegal activity, especially when they discover he had recently purchased a gun and developed an urgent need for large sums of money. However, when they receive information from a private investigator that suggests Chet may have found new evidence in his son's case, their focus is redirected. The squad must track down Chet and then put all their resources into solving Sean's case once and for all.