There currently are a variety of options to travel by night train from Toijala (Finland) to Tervola (Finland), taking between approximately 8 and 13 hours: Namely the Yöjuna 267, the Yöjuna 273 and the Yöjuna 933. These lines are operated by VR.
VR, Finland's national railway operator, runs passenger trains throughout the country, including overnight services to northern Finland.