It is Mother's Day weekend and Homeland Security informs Frank that the city is on high alert for a terrorist attack in the next 24 hours, the weapon is a biological flu virus with no vaccine. Frank and Mayor Poole disagree on how to handle the situation, Frank wanting to keep it quiet and not cause panic, and the Mayor wanting to go public. The mayor agrees to give Frank 6 hours to locate and detain the terrorists. Ultimately, through a routine traffic stop, The NYPD finds the terrorists and is able to prevent the attack. Meanwhile Danny and Jamie are at odds over a collar, a perp Danny identified to Jamie's unit, and Jamie happened to see and arrest him. Once in custody, the perp Leo offers up information to Danny on a 2 year old cold case of his, a tip about a missing 4 year old boy that still haunts Danny. Leo's information leads Danny and Jackie to a former garage attendant in the boy's building who they discover also disappeared around the same More...time as the boy. By tracking the kidnapper's mother on Mother's Day they are led to his current whereabouts, and they discover he and his girlfriend have been raising the child as there own for the past two years. Danny and Jackie bring the boy home to his real mother alive and well. The Reagans sit down to their Sunday, Mother's Day dinner and dote on Linda and Erin, and honor Mary's memory as well.