This relationship is often strained by Castle's luck in personally encountering the suspects, and sneaking in behind breaching teams even after Beckett has ordered him to remain behind; his attempts to follow them once allowing a suspect a chance to escape (although in Castle's defense this was merely because his ex-wife called him on his cell phone during the stake-out rather than any mistakes on his part). Despite this, Castle's familiarity with numerous obscure subjects often gives breakthroughs. His career yields many contacts, including a CIA agent willing to break Agency protocol by telling Castle and Beckett that their current victim was not a CIA agent.