The Longwood campus in Boston--which includes the Medical School, the Dental School, the School of Public Health and numerous Harvard-run institutes--is compact but jumbled. A half-dozen hospitals share the surrounding area with a half-dozen other colleges. All have security, but not all have police forces. Boston police, the Boston municipal police force, park rangers and transit police have stations nearby, and everyone shares responsibility for the area.

"If someone is in need of assistance, they don't really distinguish between the uniforms," Sullivan says.

8:46 a.m.--At HUPD's substation on Longwood Ave., the morning shift discusses the day. It's a small three-room station, dominated by a fish tank belonging to commanding officer Sergeant Arthur St. Andre. It's peaceful in the tank now, but once a tiny shark ate a couple of other fish. Patrolman James P. Sullivan explains that as soon as the shark got "belligerent," he had to be removed.

"We don't want a hostile environment anywhere here--even if it's in a fish tank," Sullivan explains.

Sullivan has been with HUPD longer than anyone else on the force. This week, he'll celebrate his 34th year with the department. His badge, given to the most senior officer, is number 01. Everyone else says it as "old-one."

"I guess that just comes with the badge," says the 57-year-old.

8:58 a.m.--Patrolman Stephan T. O'Connor, a two-year veteran of the force, heads out on foot patrol. The sun is just beginning to warm the chilly morning air.

Patrolling a major research facility poses some unique problems. Longwood is the land of a thousand labs--literally--where each room has an sticker warning about the flammability and toxicity of the chemicals inside. O'Connor and the other Longwood officers keep a special watch on the animal research labs, targets of numerous protests and threats.

He's only been stationed full-time at the Longwood campus for about six weeks, but loves the area.

"The time goes by a lot quicker here," he says. "If I can prevent a crime just by being visible, that's fantastic. If you prevent just a couple a week, it quickly adds up."

10:07 a.m.--As O'Connor leaves Vanderbilt Hall, where many medical school students live, he notices an ambulance parked across the street with lights flashing. Dodging the heavy morning traffic, he meets a paramedic trying to find the Mudd building. There, a man is bleeding from a head injury.

O'Connor trots towards Mudd while the medic pulls the ambulance around. Inside, a janitor is cleaning up the blood where a man hit his head after slipping. Co-workers stand nervously outside the door, waiting for news. O'Connor tries to figure out what happened while the paramedics carry the man to the ambulance--right out an alarmed emergency exit. O'Connor finishes his interviews with the alarm buzzing loudly in the background.

11:08 a.m.--In his patrol car, Sullivan loops out past Fenway Park, a Boston landmark he's been attending for over half a century.

Sullivan has seen many changes to the police department and policing in general in his three decades as a cop. When he went through the academy back in the '60s, for instance, domestic violence was never mentioned.

1:56 p.m.--While the Longwood officers continue routine patrols, one of HUPD's specialized units begins its fieldwork back in Cambridge.