Prescription: Murder is the final show in the Playcrafters Barn Theatre's 90th season, which consisted of 11 productions in as many months. (After this, Barn members are taking a well-deserved rest of a month or so before staging their next presentation in February.) I saw Friday's opening-night performance, and if any of the cast, crew, and staff are exhausted from their busy year, it certainly wasn't apparent. Everything flowed.