The following video is from Monday's Investor Beat, in which host Alison Southwick and Motley Fool analysts Lyons George and Taylor Muckerman dissect the hardest-hitting investing stories of the day.

In this segment from Investor Beat, Taylor and Lyons explain why they're keeping a close watch on shares of MarkWest Energy (UNKNOWN:MWE.DL) and Sierra Wireless (NASDAQ:SWIR).