Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Greenhill & Co. (NYSE: GHL) sank 10% today after the investment bank's quarterly results missed Wall Street expectations.

So what: The stock plunged last month on declining deal-making activity, and today's first-quarter results -- earnings sank 16% on a revenue drop of 3.7% -- only reinforce those worries. In fact, year-to-date global M&A volume has plunged nearly 30% from the fourth quarter, raising plenty of concerns about fellow boutiques Lazard (NYSE: LAZ) and Evercore Partners (NYSE: EVR), as well.

Now what: I'd look into this plunge as a possible buying opportunity. "[R]egardless of when the market again sees more normal levels of transaction activity, we are keeping our focus on the things we are able to impact," said CEO Scott Bok. "Based on what we can see internally and in the broader market, we see encouraging signs that 2013 should prove to be yet another year of meaningful market share gains for our Firm." With the stock now down about 25% from its 52-week highs, buying into that turnaround talk might not be a bad bet.

Interested in more info Green Hill? Add it to your watchlist.

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool owns shares of LAZARD. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.