Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Murder: Pennie Davis, left, was killed by a homeless petty crook who was hired by her ex-lover's son A career criminal hired a hitman to murder his stepmother for just £1,500 after she threatened to accuse him of being a paedophile. Benjamin Carr, 22, harboured a burning hatred of mother-of-five Pennie Davis, 47, during her six-year relationship with his father. He ordered fellow drug dealer Justin Robertson, 36, to kill her after she threatened to tell police he sexually assaulted young girls eight years earlier. Mrs Davis was discovered in a pool of blood by her new husband after she was stabbed while tending her horses in the New Forest. But Carr was caught after the killer accidentally left his car keys beside her body and was forced to call a friend to pick him up from the isolated spot.Justin Robertson convicted of murdering Pennie Davis in September 2014 and sentenced to life in prison with 32 years minimumVictim was found dead by her husband in a paddock in the New ForestRobertson was paid £1,500 to kill her by Benjamin Carr, her ex-lover's sonCarr wanted to stop her telling the police about sexual assault claims 
 Question:Police were quickly on the trail of those responsible and discovered Robertson, of no fixed abode, agreed to murder the victim at the request of _.

Benjamin Carr