Britannic

In Southampton in 1916, HMHS Britannic, a sister ship of RMS Titanic, has been refitted as a hospital ship for soldiers fighting in the Gallipoli Campaign. Among the nurses who are to serve aboard her is Lady Lewis (Jacqueline Bisset), who is being delivered to Greece via Naples, where her husband has become Ambassador for Great Britain. Traveling with her is Vera Campbell (Amanda Ryan), an operative of British Intelligence posing as Lady Lewis' governess. Campbell is unnerved by the voyage, having survived the sinking of the RMS Titanic four years previously, losing her husband as well.
A German spy has boarded the Britannic posing as the ship's chaplain, Chaplain Reynolds (Edward Atterton), and soon discovers that the Britannic is carrying small arms as was believed - although he is unaware that Captain Bartlett (John Rhys-Davies) has placed the small arms aboard as a means of protection against mutiny. Under the articles of war, Reynolds considers his actions against the Britannic to be legal and initiates a series of sabotage attempts to either take over the Britannic or sink her, including inciting the Irish stokers, all members of the Irish Republican Brotherhood, to mutiny.
Each sabotage attempt is foiled by Vera Campbell - with the eventual co-operation of the ship's crew. Unaware that Campbell is responsible, Reynolds finds himself growing attracted to Campbell whilst the voyage continues. As the two of them spend time together, they fall in love and Campbell has sex with Reynolds before discovering his true identity.
Reynolds blows a hole in the port side bow of the ship. The Britannic, mortally damaged, tries sailing for Kea island seven miles away, but the beaching operation causes the hospital ship to sink even faster. Campbell discovers that William, one of Lady Lewis's children, has disappeared. Reynolds helps her and they manage to get the boy to the lifeboat before it is lowered. Another massive explosion causes Reynolds to be trapped in a flooding room. Campbell helps Reynolds escape and the two of them make their way through the ship, swimming through flooded rooms, vents, grates, and corridors. They make it outside and notice a lifeboat filled with 29 evacuees getting pulled into the still spinning propellers. They watch in horror as the boat's front makes contact with the blades causing the evacuees to get thrown into the spinning blades as the lifeboat is smashed to pieces. Reynolds ties Campbell to a line that was thrown from Lady Lewis's lifeboat. Despite her protests that they both can be pulled to safety, Reynolds throws her into the sea after kissing her. Reynolds commits suicide as he is also sucked into the propellers. A few moments later, the ship groans and as she begins to roll onto her starboard side bow first, the two forward funnels and deck machinery topple into the sea as she sinks beneath the waves and disappears. A warship, HMS Victoria, arrives to rescue the survivors. Vera quotes the poem "Roll on, Thou..." from Childe Harold's Pilgrimage by Lord Byron.

Question: What does Campbell discover?
Answer: One of Lady Lewis's children, has disappeared.; One of Lady Lewis's children, has disappeared.