We present a detailed characterization of the Kepler-411 system ( KOI 1781 ) . This system was previously known to host two transiting planets : one with a period of 3 days ( R = 2.4 R _ { \oplus } ; Kepler-411b ) and one with a period of 7.8 days ( R = 4.4 R _ { \oplus } ; Kepler-411c ) , as well as a transiting planetary candidate with a 58-day period ( R = 3.3 R _ { \oplus } ; KOI 1781.03 ) from Kepler photometry . Here , we combine Kepler photometry data and new transit timing variation ( TTV ) measurements from all the Kepler quarters with previous adaptive-optics imaging results , and dynamical simulations , in order to constrain the properties of the Kepler-411 system . From our analysis , we obtain masses of 25.6 \pm 2.6 M _ { \oplus } for Kepler-411b and 26.4 \pm 5.9 M _ { \oplus } for Kepler-411c , and we confirm the planetary nature of KOI 1781.03 with a mass of 15.2 \pm 5.1 M _ { \oplus } , hence the name Kepler-411d . Furthermore , by assuming near-coplanarity of the system ( mutual inclination below 30 ^ { \circ } ) , we discover a nontransiting planet , Kepler-411e , with a mass of 10.8 \pm 1.1 M _ { \oplus } on a 31.5-day orbit , which has a strong dynamical interaction with Kepler-411d . With densities of 1.71 \pm 0.39 g cm ^ { -3 } and 2.32 \pm 0.83 g cm ^ { -3 } , both Kepler-411c and Kepler-411d belong to the group of planets with a massive core and a significant fraction of volatiles . Although Kepler-411b has a sub-Neptune size , it belongs to the group of rocky planets .