Resist the urge to high-five everyone in the cubicles next to you. Your stock may have just strapped on a rocket pack and taken off for the moon, but smart investors won't celebrate until they know that upward leap was justified. Without a fundamental basis for the bounce, these stocks can quickly make the return trip down.

Is now the time to lock in profits, or is this just the first step toward even higher valuations down the road? Let's examine several stocks that just hit the afterburners, and see whether they're truly headed into orbit.

Stock

CAPS Rating (out of 5)

Monday's Change

L-1 Identity Solutions (NYSE: ID)

***

20%

Gushan Environmental Energy (NYSE: GU)

****

20%

Antigenics (Nasdaq: AGEN)

*

16.9%

On a day when the market surged 1.4% higher even a high-flying blue chip can look like a volatile penny stock. Yet there was no specific news to account for some companies to run in the opposite direction. Chinese biodiesel maker Gushan Environmental Energy soared higher as did a number of other Chinese stocks, but other than it being down the day before more than 10%, there was no special reason it should have surged.

The devil's in the details
It's no surprise that secure document maker L-1 Identity Solutions was shopping itself to the highest bidder. Since February the biometrics leader has indicated a preference for some "strategic alternative" and just last month it said it had received some bids from interested parties, though it didn't name them.

While that's caused its share price to wax and wane over the months, the announcement that French aerospace and defense systems specialist Safran was buying the biometrics side of the business while BAE Systems was acquiring the intelligence services line sent the stock soaring. The deal is valued at $1.6 billion.

Making crime pay has become popular. Earlier this month 3M (NYSE: MMM) announced it was buying L-1's peer Cogent (Nasdaq: COGT) for $943 million.

CAPS All-Star edwjm was wary that with all the talk of acquisitions over the past ix months or so, it would make for a very volatile situation:

Caveat: This stock is popular with short sellers and is very speculative. There is also speculation about the company being involved in M&A activity. This stock is not for the faint of heart!

Making it to the old age home
However, if we're looking for gains that might not be able to hold their ground, we should consider Antigenics, which soared higher on the news that GlaxoSmithKline (NYSE: GSK) was using its adjuvant in final stage clinical trials of its experimental shingles treatment.

That doesn't mean there's anything wrong with Antigenics' adjuvant QS-21, it's just that there's still a chance for a retrenchment. There's a possibility for some substantial revenues to be realized in this market opportunity, but the treatment hasn't been approved yet. Adjuvants help boost the body's immune system so each dose requires less quantity of the vaccine. QS-21 is being considered by Johnson & Johnson (NYSE: JNJ) for use in an Alzheimer's treatment, along with nearly 20 other indications. While the euphoria over Glaxo's announcement might wear off before long, there's plenty of additional occasions for Antigenics' shares to rocket upward again.

And should Glaxo make it to market, the revenue potential will certainly help lift the stock -- and the spirits of investors -- higher.

However, highly rated CAPS All-Star member and biotech guru zzlangerhans isn't convinced Antigenics has what it takes to make for a good, long-term investment:

I'm seeing a four month high, no catalyst, and an intraday volume spike and I'm calling fake out. Antigenics may be repositioning themselves as a more conventional vaccine developer for an existence post-Oncophage. Regardless, I expect Antigenics to be bankrupt within a few more years and even if I'm wrong in the short-term, a red thumb is always a good long-term play.

You can tell us on the Antigenics CAPS page whether you agree that this is just a momentary flash in the pan that will soon fizzle out. If you want to stay on top of what's happening with this biotech, add it to your My Watchlist page where all the Foolish news and analysis about this stock is aggregated for you.

Going into orbit
Just because your stock has taken to the stratosphere doesn't mean it won't lose altitude. Markets are known for overreacting. A closer look at what's happened to your stock can give you an edge over other investors who merely follow the market's lead.

That's why it pays to start your own research on these stocks on Motley Fool CAPS, where you can read a company's financial reports, scrutinize key data and charts, and examine the comments your fellow investors have made, all from the stock's CAPS page. Then you can decide for yourself whether your stock's headed for reentry, or off to infinity and beyond.

3M is a Motley Fool Inside Value selection. GlaxoSmithKline is a Motley Fool Global Gains pick. Johnson & Johnson is a Motley Fool Income Investor recommendation. Motley Fool Options has recommended a diagonal call position on Johnson & Johnson. The Fool owns shares of GlaxoSmithKline and Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days.

True to its name, The Motley Fool is made up of a motley assortment of writers and analysts, each with a unique perspective; sometimes we agree, sometimes we disagree, but we all believe in the power of learning from each other through our Foolish community. The Motley Fool has a disclosure policy.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.