Yom Kippur, the quintessential Jewish "High Holiday", is the one day of the year that Jews you never met and never knew existed suddenly appear at shul, scan the room as if to make sure no one seeks to deny them entry, clutch a Machzor, open it to a random page until directed otherwise, and take the furthest available seat from the Aron Kodesh.
There are other such days, of course, and in a Chabad shul, the exception is the norm: Pesach, when the Israeli population of your city appears to quadruple overnight, sharing stories of travels and livelihood between cups of wine, promising all the while to come next Shabbos and vanishing without a trace day after; Chanukah, when chance shoppers happen upon the annual public menorah lighting at the local mall and stare, even as their friends move along, and maybe get sufganiyot after finally connecting with someone they know in the crowd. Yet, Yom Kippur is different - a day of supplication and introspection, of physical and spiritual exertion that does not easily lend itself to the boisterous enthusiasm with which newcomers can expect to be greeted on any other day. Still, they come.
There's the odd handful of college students, many raised reform or conservative, some exploring their faith, others reminiscing of simpler times with the family at their synagogue back home, or honoring a promise they made to their mother or bubby to be someplace Jewish on this day. Here and there doctors, lawyers, and engineers sit; professionals with intellects too rigorously trained to contemplate seriously a truth beyond their capacity to prove or disprove, and yet drawn in by the soft whisper of self-doubt, a desire for meaning and, if nothing else, nostalgia. Businessmen, still donning the conspicuous satin kippas they picked up at some bar mitzvah years ago, perhaps even their own. Working class families with children old enough to ask who they are. Seniors too infirm to bother, except when it matters. Travelers who just happened to be in town. Single, divorced, married, intermarried, tall, short, fat, thin, bald, hairy, white, black, pink, brown, gay, bi, curious and even straight, on occasion, on Yom Kippur they come. For Kol Nidre, for the morning, for a lunch break, for Yizkor, for Neilah, for the break fast, and maybe for all of it, of all the days in the year, on this day they come.