There is an old show business saying that comedy is just tragedy plus time, which I've always thought was odd. Tragedy often is when comedy is needed most.

I've been a comedian for more than a decade, since my humble beginnings at the now-defunct Annapolis Comedy Club, and know that being a comic isn't always a laugh a minute. Comedians have their share of professional challenges; the "tough room" is among the biggest. From unruly audiences to inadequate sound systems, any number of things can make it hard to win over a crowd.

At 8 p.m. on Sept. 14, 2001, I faced the toughest of tough rooms. I followed a terrorist attack.

When the lights went up at DC Improv that Friday night, I parted the curtain, walked onstage and faced a sea of roughly 35 people.

Considering all that had happened that week, we were lucky anyone at all was there, but it didn't change the fact that this was a small crowd. Making a thousand people laugh is easy, but it is real work making three dozen laugh -- particularly in so spacious a room and at such a sorrowful time.

Months earlier, I had been booked to work for a week at the club with national headliner Wendy Liebman. I eagerly counted down the days to our first show. It was to be on Tuesday, Sept. 11, 2001.

Twelve hours before show time, the planes crashed, the twin towers collapsed and the Pentagon burned. There is nothing I can say about that day that hasn't already been said a thousand times before and more poignantly. We were a nation under attack, unsure of why or of when and where the terrorists would strike next.

As a precaution, all commercial air traffic was stopped. The only thing on television was news -- round-the-clock and commercial-free. With people staying home for safety's sake and many streets in the capital barricaded, many Washington bars and restaurants were dark.

That Friday, DC Improv managers John Xereas and John Johnson decided to open the club's doors. It was a risky move, so instead of the usual two shows, they opted for one. Only three days after the attacks, it was unclear whether anyone was ready to laugh again. The room either would be empty or it would be packed with people needing relief from the continuous news and the acute anxiety.

For comedians, a Friday early show is one of the best shows of the week. The crowd typically fills the room to capacity, having already had a couple of after-work drinks, and is ready to start the weekend with a few laughs. In this respect, Washington's first comedy show after 9/11 had everything going for it -- except for the nearly empty room staring back at me and those 35 people waiting to be entertained.

My nerves were shot because a lot rides on the opening act. A bad start can taint an entire show, and this was one evening that deserved to be great. When I pulled the microphone out of its stand, I thanked the people for coming and said I hoped they would have a good time because that's what the terrorists don't want us to have.

The crowd applauded patriotically, so I went on. Unsure of how they would react to edgy material, I stayed with my tamer stuff.

"I had to put my dog to sleep this week," I said, to which the audience predictably gives a sympathetic groan, "which was hard because he's an insomniac." They laughed. I kept going.

"My other pet cheers me up -- he's a pet veal calf, which is a great pet to have in an apartment because he doesn't need a lot of room to run around."

This joke usually delivers, but not that night. I marveled at how fast a comedy club can become a library.

And so it went, the crowd's laughter and I playing cat and mouse for the rest of the night. The other two comedians -- feature act Al Goodwin and headliner Joe Recca, replacing Liebman (who couldn't fly in from Los Angeles) -- got similarly atypical responses. Both are great comedians, which only compounded the mystery. It was a weird show, where jokes that normally worked didn't and those that normally didn't did.

Afterward, Mike Noble, a videographer taping my performance, interviewed audience members as they left. Some were from Washington, but many were far from home. A canceled medical conference left two North Dakota ladies stranded at a D.C. hotel. They wore matching Stars and Stripes kerchiefs to the club.

"We have not been able to get out of the city," said one, "and we've been bumped out [of return flights] all week. We figured tonight would be the night to have some fun."

"It was really nice," her friend added. "The drinks were strong, food was great, comedians were wonderful. Now we have to go back to reality. We have to see if we're going to get home."

A Washingtonian named Cindy admitted she had been skeptical about her friends' invitation to go to a comedy show so soon after the terrorist attacks.

"You feel guilty coming out, having a good time and listening to jokes," she said, "but . . . it was very sensitive in the beginning. It made you feel like you were bonding here with people you didn't even know. It just made you laugh and kind of forget about stuff. It felt like things were okay."

It was good to learn that the audience found helpful a show I'd thought was largely unsuccessful. It was better still when for unfathomable reasons the following night's show was standing room only and every joke worked. Even my veal-calf joke.

In the five years since, I've performed in venues ranging from fire halls to Times Square, but that single show on Sept. 14 will forever be special. It was a tough room but a great audience. The people put aside their fears for the sake of a few laughs on a Friday night. That was truly noteworthy.

For weeks after 9/11, humorists of every stripe struggled with knowing when it was safe to joke again. David Letterman was the first of the late-night comedians to go back on the air after the attacks, and he not only waited a week but also did shows that were full of emotion and joke-free. Like many comedians, Liebman didn't perform for several weeks. Comedians found it difficult to strike a balance between levity and grief, irreverence and solemnity.

But, like flowers blooming after a wildfire, laughter returned. Comedians found new targets for their jokes, and humor became one of America's best defensive weapons.

Tragedy plus time? I don't buy it. Tragedy is just comedy's unfortunate opening act.