A woman had testified in court of seeing Nicholas Fomby-Davis stagger into a popular corner store and collapse before her eyes. I have to find her. Maybe she would retell her story for Globe readers — and do it on video. The only information I have about her was what turned out to be an erroneous name — Nadine — and the name of her street, Speedwell. At around 8 a.m., I begin trekking up and down the street in search of her. When someone answers the doorbell, I repeat the same line: “This is going to sound strange. But I’m looking for a black woman, heavyset, with dreads. Dark-skinned?” Usually I am met with blank stares. Others are certain they know her. They point to a green house, then a blue house, or simply down the street. Finally, feeling unlucky, I head back to my car, making one more stop on the way, at a house on the corner, just a few blocks from where Nate and Trina Davis live. I knock. A woman, gloriously plump, dark-skinned, and wearing dreadlocks, pokes her head out of the third-floor window. Turns out her name is actually Nichole. I check my list. I had knocked on two dozen doors that morning. Hers was door number 24.