Hugger Mugger by Robert B. Parker

Hugger Mugger (Spenser) - Spenser is asked by the owner of Three Fillies Stables, Walter Clive to investigate the shooting of their horses and the attempted shooting of their prize horse, Hugger Mugger.  When Clive is murdered, his daughter Penny fires Spenser.  However, he is later rehired to investigate the will by Clive’s mistress.