Belle is a large tank engine with water cannons who is part of the Search and Rescue Team stationed at the Sodor Search and Rescue Centre.
When Belle first arrived on Sodor, she helped Thomas and Percy put out a fire at the old farm shed. Belle later advised Sir Topham Hatt to bring Flynn to Sodor. When the Sodor Dieselworks was on fire, Belle and Flynn put out the fire just in time.
Belle later tried to befriend Toby when she learned that they both had bells. At first she did not understand that Toby was an older engine that may not like the same things she does, but she soon realized her mistake and they are now firm friends.
Belle attended the welcome party for Sir Robert Norramby and tried to help in the search of Stephen when he went missing. When some railway inspectors questioned whether The Fat Controller needs two fire engines, she and Flynn became worried. She beat Flynn to two consecutive fires, but tried to comfort him when he subsequently became depressed. She stayed on guard at the firework display at Ulfstead Castle when Flynn refused to do it; when Flynn was called to another fire at Brendam Docks, they both realised that Sodor really does need two fire engines after all.