It's January and winter is biting hard. Mac is asked to investigate the brutal murder of a homeless man in London by his grieving daughter. Meanwhile two of Mac's police colleagues are looking into the suspicious death of a Cambridge history professor. Their paths cross and they realise that the two deaths are somehow linked. During the investigation Mac meets someone from his past, someone he'd hoped he'd never see again. The Tiger, the most fearsome and violent criminal that Mac had ever dealt with, is once again loose on the streets.