"Thomas, I'd like you to Meet Emily."
-The Fat Controller introducing Thomas to Emily.
Emily The Stirling Engine is the forty-fourth book in the Railway Series.
There is a new engine on the Fat Controller's railway. She is a Stirling Single named Emily. She stole Annie and Clarabel from Thomas before receiving her own coaches. She is now part of the team on the North Western Railway.
On her first day, Emily takes Annie and Clarabel, which makes Thomas cross. He eventually forgives her after saving him from hitting a broken down Oliver.
Emily is scared of a monster in Black Loch.
Thomas, Percy and Henry are sent to collect coal trucks and take them to the harbour. Henry is feeling ill but Thomas and Percy do not believe him and leave him a long line of trucks.
Cyril, a fogman, puts detonators on the tracks to warn engines of oncoming mist. Sir Topham Hatt replaces him with a fog horn, which turns out to be more trouble than it is worth.