BOSTON — An emotional and improbable and cardiac-arrest-inducing two games in TD Garden ended like this: a small pocket of Knicks fans chanting obscenities at the Celtics after the rest of the crowd dispersed, a Boston cheerleader bawling in the hallway with her glammed-up coworkers chasing behind and, finally and fittingly, a fire alarm in the arena that started during postgame interviews and prompted mass evacuation. 

“Nobody else worried about this?” Josh Hart said as the alarm belted during his news conference. 

The threat cleared within minutes, it turned out. More of a false alarm than a serious threat. But the Celtics should still be worried. 

Very worried.