Biggest Mysteries of 2014

The stories that captivated our attention and baffled the mind.

— -- Horrifying crimes and the bizarre behavior of a strange world leader captured the public's imagination and piqued curiosity.

One story stood apart from all the rest, however, as neither science nor technology could help solve the world's biggest mystery: How could a jetliner full of people, in our intensely scrutinized and electronically tracked world, simply disappear?

Have a look back at some of the most mind-boggling stories of the past 12 months.

1. Where is the missing plane?

2. Where are the missing girls? Boko Haram and #bringbackourgirls

During a night in mid-April, 276 teenage girls were kidnapped by an Islamic jihadist group in Chibok, Nigeria, and the news of their capture prompted international outrage. Word of the attack spread via social media with the hashtag #bringbackourgirls. About 50 of the girls have been able to escape their captors, who have been identified as members of the militant group Boko Haram, and though there have been rumors that the girls could be released as a result of an exchange with the Nigerian government, no such deal has come to fruition. An estimated 219 girls are still missing.

After allegedly killing a Pennsylvania state police trooper, 31-year-old Eric Frein was able to hide from local and federal authorities for nearly seven weeks. The survivalist hid in the sprawling woods of the Pocono Mountains and experts believe that he was able to evade capture for so long because he had planned ahead. Searches of his computer showed that he had prepped by researching SWAT raid tactics, police cell phone tracking technology and how best to hide caches -- small duffle-type bags that hunters use to hide food and supplies in the wilderness. He was finally found at an abandoned airport hangar the day before Halloween and surrendered without a struggle. All told, the manhunt lasted 48 days and cost the state more than $11 million.