Investors returned from the long Labor Day weekend in a bearish mood.

New developments in the North Korea-U.S. conflict and a string of big-industry deals kept Wall Street under pressure. The Dow Jones Industrial Average was down 1.07%, or 234 points, the S&P 500 fell 0.76% and the Nasdaq slid 0.93%.

Here are five things that caught TheStreet's attention with an eye towards Wednesday's trading session. 

Volatility Spikes

The Volatility Index (VIX), otherwise known as the fear index, spiked more than 38% to 14 by Tuesday afternoon. That was its largest daily increase since Aug. 10.

The threat of military action from North Korea spiked over the weekend break after the ready-to-strike authoritarian nation successfully conducted its sixth nuclear test on Sunday, Sept. 3. Worries over North Korea had receded in recent weeks as headlines became crowded by a terrorist attack in Charlottesville, Virginia, in mid-August and Hurricane Harvey's path of destruction across Texas and Louisiana last week.

South Korea's defense ministry said Monday, Sept. 4, that North Korea is preparing the launch of another intercontinental ballistic missile, one that could be fitted with a nuclear warhead. North Korea launched its first two ICBM tests in July.

Bank Stocks Tank

Financials were the worst performers on Tuesday with Goldman Sachs Group Inc. (GS - Get Report) shares taking a large chunk out of the Dow. Other laggards in the financial sector included Bank of America Corp. (BAC - Get Report) , Wells Fargo & Co. (WFC - Get Report) , JPMorgan Chase & Co. (JPM - Get Report) , HSBC Holdings PLC (HSBC) and Citigroup Inc. (C - Get Report) . The Financial Select Sector SPDR ETF (XLF - Get Report) declined by 2%.

Citigroup is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells C? Learn more now.

For the rally to resume, in an ideal case financials lead. 

Meanwhile, the Federal Reserve is about to become a bigger risk. 

Investors Flock to Treasuries 

Worries over North Korea sent demand for safe-haven assets such as Treasuries skyrocketing. The yield on the 10-year note was down roughly 9 basis points to 2.068%, its lowest level since November 2016, while the 30-year bond was down to 2.69%.

Apple Lags

When Apple (AAPL - Get Report) shares under-perform during a stock market rout, it's a red flag. Apple shares fell 1.2% on the session compared to the S&P 500's 0.76% gain. 

Apple is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells AAPL? Learn more now.

Small-Cap Stocks Continue to Perform Poorly

The iShares Russell 2000 ETF (IWM - Get Report) , which measures the performance of small-cap stocks, under-performed the S&P 500 slightly on the session. Over the past three months, the ETF has gained a mere 0.2% compared to a 1.2% gain for the S&P 500. 

More of What's Trending on TheStreet: