There currently is one option to travel by night train from Narvik (Norway) to Stockholm (Sweden), taking approximately 19 hours: Namely the 93 operated by SJ.
The Swedish Railway SJ operates night trains daily throughout Sweden, covering long distances and serving remote areas.
The night trains include seating cars, couchettes, and sleepers. The sleeper cars provide compartments for two or three people as well as single compartments. Some routes also offer Deluxe compartments with private bathroom facilities and shower.
Each sleeper compartment has a washbasin. The Deluxe option additionally provides a private bathroom with shower.
The couchettes offer space for up to six people with access to provided bedding and toilets in the carriage corridor. The middle berths fold up during the day to create seating areas. Compartment options include women-only, men-only, or mixed assignments. Private couchette compartments are available for travelers with pets upon request.