 He is sentenced to life in prison for murder after he killed Michael to avenge Jodie's death.Derek Kok portrays Sze To-Hoi (司徒凱), known as Dog Head (狗頭), the sergeant of CIB's A Team.He is addicted to gambling and is indebted to Yee Fung, so he is forced to help Mok Yat-lit deal with triad matters.