  Changing-look active galactic nuclei (CL-AGN) have been observed to change
optical spectral type. Mrk 1018 is unique: first classified as a type 1.9
Seyfert galaxy, it transitioned to a type 1 before returning to its initial
classification after approximately 30 years. We present a high-cadence
monitoring programme that caught a major outburst in 2020. Due to sunblock,
only the decline could be observed. We studied X-ray, UV, optical, and IR
before and after the outburst to investigate the responses of the AGN
structures. We derived a u'-band light curve of the AGN contribution alone. The
flux increased by a factor of the order of 13. We confirmed this in other
optical bands and determined the shape and speed of the decline in each
waveband. The shapes of H beta and H alpha were analysed before and after the
event. Two XMM-Newton observations from before and after the outburst were also
exploited. The outburst is asymmetric, with a swifter rise than decline. The
decline is best fit by a linear function, ruling out a tidal disruption event.
The optical spectrum shows no change approximately 8 months before and 17
months after. The UV flux increased slightly after the outburst but the X-ray
primary flux is unchanged. However, the 6.4 keV Iron line has doubled in
strength. IR data taken 13 days after the observed optical peak show an
increased emission level. Calculating the distance of the broad-line region and
inner edge of the torus from the supermassive black hole can explain the
multi-wavelength response to the outburst, in particular: i) the unchanged H
beta and H alpha lines, ii) the unchanged primary X-ray spectral components,
iii) the rapid and extended infrared response, as well as iv) the enhanced
emission of the reflected 6.4 keV line. The outburst was due to a dramatic and
short-lasting change in the intrinsic accretion rate. We discuss different
models as potential causes.
