NOT EXACTLY HARPER LEE: Boyd was distressed. It was 7 p.m. on Wednesday night and he had lost the scent, and had no idea where to pick it up again. To add to his frustration, his thoughts wandering back to the words the vagrant in the park had muttered. He took out his notebook and placed it on his desk, under the yellow light of his lamp. Smoke from a Lucky Strike curled up from his ashtray. Charles Mingus played from an old stereo on a shelf. He decided to write down the vagrant’s words, just in case. As Boyd said the words to himself again, something struck him. ‘A daring boy’… could that be… yes, of course! Darren Boyd! He was amazed he hadn’t realized it already. But what does the rest of the message mean? Boyd took a sizable gulp from a glass of scotch, opened his laptop and typed in “To mock a killing bird” into the search box. Boyd was for once almost visibly excited when he read the results – “To Mock a Killing Bird” is an original improv murder being put on by the Extemporaneous Theatre Company, or ETC. He scribbled furiously in his notebook. Birmingham Festival Theatre, showings Dec. 26, 27, 30 and 31 at 8 p.m. Tickets $15. www.extemporaneoustheatre.com. He glanced up at the clock—he had just minutes to spare.