You can use
@startuml
rectangle a {
rectangle b
rectangle c
rectangle d
b -[hidden]-> c
c -[hidden]-> d
}
@enduml
http://www.plantuml.com/plantuml/uml/SoWkIImgAStDuIfAJIv9p4lFILL8LAZcKb10y9DGUCael1GWBqb1DpeZCoKbDIzMrmuidumi0bHJo-MGcfS2j0K0
But this is really a hack, and you should not abuse of hidden arrows.