The last clue could read:

"You've all worked hard, you've put up a good fight.

Let's get to that cake now. Let's all take a bite.

Please proceed with caution and get ready to bellow

"Happy Birthday to You" to our birthday fellow

(or, if the party is for a girl, use this rhyme for lines three and four: Please proceed with caution after playing this game, and be ready to sing to today's birthday dame)

The cake is now sitting in a room where we eat.

No, not the kitchen, the room with the seats.

Note: Mystery missions are fun to coordinate, but if you'd rather have someone else do the prep work consider buying a pre-packaged mystery party kit, like the ones sold by companies such as American Girl ().

The Cake

So what should that cake look like?

It could be shaped like a trench coat, magnifying glass, a question mark or a large fingerprint with swirled icing on top.

You could also make crime-scene investigation tape out of yellow and black fondant and drape it across a cake.

Or have a bakery airbrush the silhouette of a shadowy figure carrying a briefcase. To get the same look at home, cut the shape out from black rolled fondant. That same spy could creep across a book-shaped cake to emphasize spy books rather than movies.

If the birthday kid is a James Bond fan, you could top the cake with a "007" or "009" or "010" or whatever age the child is turning.

Your child's spy birthday party might be focused on a particular movie or book. In those cases, go with a cake that depicts a character or symbol from the story, like a cake celebrating Disney's action-hero dog, Bolt.

Other Food

If you also plan to serve savory snacks, give regular food spy-related names, like Agent Apples, Fingerprinted Fish Sticks, Undercover Onion Rings, Double Agent Dogs (two hot dogs in one bun) and Top Secret Sandwiches.

Party Favors

Instead of generic goodie bags, make each child a spy kit complete with a small notepad, a pencil, dark sunglasses, Groucho-style disguise glasses, a magnifying glass and lie detector cards that supposedly determine if you're telling the truth based on the temperature of your thumb.

You could add trick candy, such as Pop Rocks, to the bag, too.

Real Spy Parties

Want to see how a real spy party turned out for one 9 year old girl? Blogger Amy J. of Cazier Corner threw a spy party for her daughter Sydney, complete with crime-scene tape for decorations and invitations printed backwards so guests had to hold them up to a mirror to read them.

The kids went on a treasure hunt during the party but had to fingerprint their clipboards before beginning.

Amy's idea for a cake decoration was clever and simple: Write the words "I spy" in large frosting letters, then place a plastic magnifying glass over the top of them.

Another mom, Lisa Moore in Colorado, threw a spy party for her 9-year-old son, Cameron. Lisa, who writes the blog Moore Minutes, decorated with bright, cheerful colors to make the party look fun and youthful. She drew chalk footprints leading to the front door for guests to see as they arrived.

Along with lots of treats, the guests were given water bottles labeled "Secret Agent OO7," "Secret Agent 008" and so on.

The cake was shaped like a round bomb with a Fourth of July sparkler sticking out of it.

The kids were sent on a scavenger hunt that led to a tree where Cameron's big present--a new bicycle--was hanging.

Whether you plan an all-out party filled with spy-related activities or just want to put up a few decorations and pop in a movie, enjoy your mystery-minded birthday kid's big day.