On his trip to the Mainland, Thomas discovers a strange place called the Steelworks, where he befriends two mysterious engines named Frankie and Hurricane. However, he realizes they aren't quite what they seem. Frankie and Hurricane soon put Thomas to work and prevent him from leaving the Steelworks.
Frankie is a devious diesel engine. She is very controlling and sometimes rude. She only acts the way she does is because she wants help.
Frankie is based on a Hudswell Clarke 0-6-0 diesel shunter which worked at the Manchester Ship Canal. No. 4002 Arundel Castle, affectionately known as "Billy", is preserved in working order by the East Lancashire Railway Diesel Group. Sister locomotive No. 4001 Alnwick Castle is also preserved as a static non-operational exhibit at the Winfields Store site at Rising Bridge.
Frankie is painted teal and black with gold lining. She has red and gold nameplates on either sides and "M.S.C." written above her face. The number "4002" is written in yellow on her front bufferbeam.
- Frankie is the first engine of several things:
- The first female diesel engine in the television series since Mavis, and the first female diesel to originate in the television series instead of the Railway Series.
- The first female main antagonist in a special
- The first antagonist whose intentions are not meant to be cruel or evil.
- The first engine to cry in the CGI series.