If you sit on the front stoop of your building practically every day for 25 years, the way James Rudnick has, people expect you to know what is happening on the block. So every day, people stop and ask Mr. Rudnick  Jimmy from Union Street, as he’s known here in Park Slope  what he knows about the white-painted stroller that has been padlocked to a parking sign on the corner of Union Street and Sixth Avenue since the beginning of the month.

Sometimes the passers-by look curious; sometimes they are distraught, concerned by the three plastic roses  peach, pink and red  tucked behind the straps, which give the stroller the distinct look of a memorial commemorating some grim accident.

Mr. Rudnick does not, in fact, know the origins of the stroller, although he knows one thing: if a child had been killed in traffic on a corner anywhere nearby, he would know. “Or someone we know would know,” added his wife, Sara Bernstein, who sat beside him on the stoop on Monday. “But we would know!”

What they do not know, what no one seems to know, is who went to the effort of painting the stroller that uncomfortably chalky Mylanta white  taking a paint brush to the cup holder, the bag zipped in back, the mesh basket below, even the chain and padlock attaching it to the parking sign.