At first glance, a ghost tour around Harvard Square in the midst of a budding hurricane might not scream romance. But for Rosana Gambino and Jerilyn Sawyer, these elements would set the stage for a marriage proposal over a month in the making.

Last Sunday Gambino proposed to Sawyer through a flash mob staged in front of Cambridge's Old Burying Ground.

The mob started with a single person clapping to the tune of Chris Brown's "Forever," and quickly ballooned into a half a dozen people dancing on the streets of Cambridge. The routine went off without a hitch, concluding with Gambino getting down on one knee and proposing with 'Marry Me' by Bruno Mars playing in the background.

When Gambino thought about proposing, she took into account Sawyer's love of Halloween, as well as the fact that their first date took place on a ghost tour. About a month ago Gambino reached out to Cambridge Haunts tour organizer Sam Baltrusis and told him of her plans to propose.

Baltrusis said when he received the call, he "was so excited I dropped the phone."

With the tour group on board, Gambino proceeded to enlist the help of friends, who rehearsed throughout the month of October in preparation for the special day. She rallied dancers from her school, Northeastern University, to perform, had a choreographer friend create the routine, and even invited her family to attend.

The burial ground backdrop, on a night three days before Halloween, created a spooky and haunted atmosphere. Although Hurricane Sandy provided an unexpected plot twist, Baltrusis said it added to the ambiance of the event.

"A lot of the alleged hauntings happen when it's raining," Baltrusis said. "Rain brings out the spirits."

And to top off this storybook proposal, amidst cheers from the crowd, Sawyer immediately said yes.