http://abcnews.go.com/WN/story?id=4193271

Watch "World News with Charles Gibson" TONIGHT at 6:30 p.m. ET, for Bill Weir's full report.

How does an undocumented immigrant cross into the United States from Mexico? How does the U.S. Border Patrol police the long border? What happens, in a typical 24-hour period, along this fascinating, dangerous, and politically critical patch of land?

'World News' on the Border: Inside Look at Drug and Human SmugglingBorder Guards Chase Smugglers Along
As part of our series, "The Real 24: One Day in the Life," ABC's Bill Weir takes a closer look at all those questions — after he and an ABC News team spent a recent day and night on both sides of the frontier.

Over the course of 24 hours, Weir and his team visited border towns in Arizona and Mexico. They spoke with Mexican citizens planning to cross into the United States, and with many who had just been deported. They also spoke with U.S. Customs and Border Patrol agents, and residents in a small Arizona border town, to explore how the effects of immigration — both legal and illegal — are felt every hour of every day.

Watch these sneak previews of the full report, Monday, Jan. 28, 6:30 p.m. ET:

Click here to go on night duty with the U.S. Border Patrol.

Click here to take a chopper ride along the U.S. border.

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