"Hard Tango" is a term used by Terry McCaleb to describe the sensitive and often conflict-riddled relationship between the FBI and local police. Whenever the FBI are called in to a case, whether to take over or to consult, the locals often perceive it as heavy-handed and aggressive. Sometimes it actually is. At other times the FBI takes pains to not step on toes, but that does little to alter the perception of local police. It frequently manifests in one agency hiding vital information from the other, thwarting the progress of investigations. There can be similar jealousy and conflict between different local police agencies, and even between investigators in the same agency. The troubled relationship between the FBI and the LAPD plays out in virtually all of the cases investigated by Harry Bosch , but it is complicated by the fact that his ex-wife was former FBI and Terry McCaleb became a good friend.