The Square Root of Murder (Professor Sophie Knowles)

divided the sales room from the rest of the shop. Today, if you took the long view, you could make out a large stem of purple irises springing from a background of many shades of green. I thought of the staggering number of small beads it must have taken to make up the design.
    And Ariana thought it took patience when I worked through a mere six pages of mathematical proof.
    Ariana’s customer was an older woman in shorts that would have looked better on Lucy. She carried a small tray around the shop while Ariana helped her add selections to it.
    “I need five small blue ones,” the woman was saying as Ariana smiled “hello” to me.
    “Five small blue ones,” Ariana echoed, setting the beads in the woman’s felt-lined tray.
    “And one large purple,” the woman continued.
    Ariana plucked a large purple bead from a cloth-lined organizer on a table that held a set of them in different sizes. “There you go.”
    “Maybe I only need four small blue ones,” the woman said.
    Ariana removed one of the blue beads. “How’s that?” she asked.
    The woman frowned and shook her head. “Mmm. I’m not sure now.”
    I turned away. There was a reason I wasn’t a shop owner. I’d have had choice words for this customer and sent her packing to some other bead store. Not good for business.
    I did enjoy filling in for Melissa, Ariana’s part-time employee, now and then, however. But even then, I preferred stocking inventory and wiping down cases to dealing with customers, probably because I was hopeless at offering design help unless the person was trying to model an arithmetic series in a bracelet.
    I amused myself by looking around the shop. Ariana had sectioned off one area with a new line of crafts products, many related to scrapbooking and stamping. I turned rotating racks of two- and three-dimensional stickers, rolls of ribbon, glue cartridges, stencils, novelty rubber stamps and pads, and small cans of spray paint. I knew it had been hard for Ariana to make the decision to move away from a beads-only shop, but the need to diversify to stay in business had taken over.
    About ten minutes and nine other changes of mind later, the woman left the store with a tiny bag of beads.
    “You’re so good with pesty people,” I said to Ariana.
    She smiled. “Lucky for you.”
    Whatever that meant. I poked her in the arm in case she’d just insulted me.
    With the luxury, or maybe the curse, of an empty store, Ariana and I sat on folding chairs in front of a glass counter that held a more expensive inventory of gems and charms.
    “I’ll be you and you be the dean,” Ariana said.
    I was nervous already. “I’ll give it a try.”
    “I found something very interesting as I was cruising online, Dean Underwood,” Ariana said.
    “I would say ‘browsing the Internet’ not ‘cruising online’,” I corrected.
    Ariana rolled her eyes. “Okay, browsing the Internet, but try to concentrate on the big picture, Sophie.”
    “Sorry. Can I get a bottle of water from the back?”
    Ariana checked her watch. “Not for another ten minutes. We need to get this started.”
    “You’re cold.”
    “As I was saying, Dean, I was looking up some examples of statistical surveys that I could use in class and I found many of them were carried out in New York City in the sixties. Studies of marijuana use, disorderly conduct, trespassing, that kind of thing, and I was so surprised to see your name come up.”
    “I don’t know what you mean,” I said, playing a thunderstruck dean.
    Ariana gave me an exaggerated, skeptical look, then waved her hand dismissively. “It’s probably a different Phyllis Underwood, a sociology major who graduated in nineteen sixty-eight. One of your classmates?”
    She was good. “I give up,” I said lowering my head and weeping.
    “Wasn’t that easy?” Ariana said.
    “I see where you’re going with this. I just let her tell me exactly what it was. And if I really am wrong, well, I won’t be any worse off than I am now.”
    “You go, girlfriend,” my mentor said.
    If only the dean would follow the script, I’d be one happy mathematician.
    A tinkling sound interrupted us. Two customers, a mother and teenage daughter, entered. I hoped they’d be easier to deal with than the old woman in shorts.
    I left Ariana to her business and went through the sparkling curtain to the back. I grabbed a bottle of water from the fridge and sat down to check my emails and phone messages. Way too many emails for